When at last I've had my fill, I rock back on my haunches and gaze across a clump of papyrus to the trees and waving gra.s.ses beyond the river. To the creatures who inhabit this green and alien world, I am but a walking source of meat, and everywhere I look, I imagine teeth waiting to devour me. With sunrise came the noisy chatter of birds, and when I look up, I see vultures tracing lazy loops in the sky. Have they already marked me for their next meal? I turn upriver, toward camp, and see the clear trail of footprints I've left along the bank. I remember how easily Johnny tracked even the faintest paw prints. My trail will be as glaring as neon for him to follow. Now that it's daylight, he'll be hunting me because he can't afford to let me live. I'm the only one left who knows what happened.

I rise to my feet and continue to flee downstream.

I can't allow myself to think of Richard or the others. All I can focus on is staying alive. Fear keeps me moving, pushes me deeper into the wild. I have no clue where this river leads. I recall from the guidebook that the rivers and streams of the Okavango Delta are fed by rainfall in the Angola highlands. All this water, which annually floods these lagoons and swamps from which so much wildlife magically springs, will eventually empty into the parched Kalahari Desert. I glance up to gauge the direction of the sun, which is only now lifting over the treetops. I am walking south.

And I am hungry.

In my knapsack I find six PowerBars, 240 calories each. I remember tucking them into my suitcase in London, just in case I couldn't abide the food in the bush, and I remember how Richard mocked my unadventurous palate. In an instant I devour one of the PowerBars and have to force myself to leave the remaining five for later. If I stay near the river, at least I'll have water, an endless supply of it, even though it surely carries a host of diseases I can't even p.r.o.nounce. But the water's edge is a dangerous zone where predator and prey so often meet, where life and death converge. At my feet is an animal's skull, bleached by the sun. Some deer-like creature that met its end here on the riverbank. A line of ripples disturbs the water, and a crocodile lifts beady eyes to the surface. This is not a good place to be. I veer away into the gra.s.s and find a pathway has already been trampled here. Tracks stomped in the dust tell me that I am following in the footsteps of elephants.

When you are afraid, everything zooms into sharp focus. You see too much, hear too much, and I'm overwhelmed by a rapid click-click of images and sounds, any one of which might be the only warning of something that will kill me. That must all be processed at once. That swaying of the gra.s.s? Merely the wind. The blur of wings swooping above the reeds? A fish eagle. The rustling in the underbrush is merely a warthog rambling by. Tawny impala and the darker shapes of Cape buffalo move along the horizon. Everywhere I see life, flying, chattering, swimming, feeding. Beautiful and hungry and dangerous. And now the mosquitoes have found me and are feasting on my blood. My precious pills are back in my tent, so add malaria to the list of ways to die, along with being mauled by a lion, trampled by a buffalo, drowned by a crocodile, and crushed by a hippo.

As the heat builds, the mosquitoes become relentless. I wave at them maniacally as I walk, but they thicken into a biting cloud that I cannot escape. In desperation, I'm driven back to the riverbank where I scoop up handfuls of mud and slather my face and neck and arms. The silt is slimy with decaying vegetation and the smell makes me gag, but I slap on thicker and thicker layers until I'm encased in it. I rise to my feet, a primeval creature emerging from the muck. Like Adam.

I continue on the elephant path. They, too, prefer to travel alongside the river, and as I walk I spot other prints that tell me this route is used by a mult.i.tude of different creatures. This is the bush equivalent of a superhighway, all of us traveling in the footsteps of elephants. If impala and kudu walk this way then surely lions do as well.

Here is yet another killing zone, where predator and prey find each other.

But the tall gra.s.s on either side of me hides just as many threats, and I don't have the energy to thrash my own path through dense bush. I must move quickly, because somewhere behind me is Johnny, the most relentless predator of all. Why did I refuse to see it? As the others were taken down one by one, their flesh and bones fed to this hungry land, I was blind to his game. Every look Johnny gave me, every kind word, was merely a prelude to a kill.

As the sun reaches its height, I am still trudging the elephant path. The mud dries to a hard crust on my skin and clumps of it crumble into my mouth as I eat a second PowerBar, and I devour it, grit and all. I know I should conserve my food supply, but I'm already famished and the ultimate tragedy would be to collapse dead, with food still in my knapsack. The trail veers back toward the water's edge, where I come to a lagoon so black and still that a twin sky is reflected in its waters. The heat of midday has silenced the bush; even the birds have gone quiet. At the water's edge is a tree where dozens of strange, pendulous sacs hang like Christmas b.a.l.l.s. In my heat-crazed exhaustion, I wonder if I've stumbled upon a colony of alien coc.o.o.ns, left to incubate where no one will discover them. Then a bird flutters past and vanishes into one of the sacs. Weaverbird nests.

The water of the lagoon stirs, as if something has just awakened. I back away, sensing evil here, waiting to trap the unwary. I feel its chill at my back as I retreat, once again, into the gra.s.s.

THAT EVENING, I WALK straight into the elephant herd.

In bush this thick, even something as large as an elephant can take you by surprise, and as I stumble out of a stand of acacia trees, suddenly there she is in front of me. She seems just as startled as I am and gives a trumpet of alarm so loud that it seems to blast straight through me. I'm too shocked to run. I stand frozen, the acacias at my back, the elephant facing me, standing just as still. As we stare at each other, I see ma.s.sive gray shapes moving all around me. A whole herd of them are rattling the branches, snapping off twigs. They know I am here, of course, and they pause in their feeding to warily eye the mud-caked intruder. How little effort it would take for any one of them to kill me. A swat of the trunk, one ma.s.sive foot on my chest, would rid them of this threat. I feel them all studying me, weighing my fate. Then one elephant calmly reaches up, breaks off a twig, and slides it into her mouth. One by one, they resume feeding. They have judged me, and issued their reprieve.

Quietly I slip back into the brush and move toward the cover of a majestic tree that towers above the acacias. I clamber up the ma.s.sive trunk until I'm high enough to perch safely above the herd, and I settle into the crook of a branch. Like my primate ancestors, I find safety in the trees. In the distance, hyenas cackle and lions roar, a warning of the coming battle at nightfall. From high in my perch, I watch the sun set. In the shadows below my tree, elephants continue to feed, rustling and shuffling. Rea.s.suring sounds.

The whole night comes alive with screams and roars. The stars wink on, crystalline bright in a black sky. Through arching branches I spy the constellation Scorpio, which Johnny pointed out to me on the first night. It's just one of the many things he taught me about living in the bush, and I wonder why he bothered. To give me a fighting chance and make me more worthy as prey?

Somehow I have outlasted all the others. I think of Clarence and Elliot, the Matsunagas and the blondes. Most of all I think of Richard and what we once had together. I remember the promises we made, and the nights when we'd fall asleep with our arms around each other. Suddenly I am weeping for Richard, for all that we once had, and my sobs are like one more animal call in this noisy nocturnal chorus. I cry until my chest aches and my throat is raw. Until I am so exhausted that I am limp.

I fall asleep the way my ancestors did a million years ago, in a tree, under the stars.

AT DAWN ON THE fourth day, I unwrap the final PowerBar. I eat it slowly, each bite an act of reverence for the holy power of food. Because it is my last meal, every nut, every flake of oat is a joyous explosion of flavor that I never truly appreciated before. I think of the many holiday feasts I've gorged on, but none was as sacred as this meal, eaten in a tree as the sky blooms gold with the rising sun. I lick the last crumbs from the wrapper, then clamber down to the riverbank, where I drop to my knees as though in prayer, and drink from the rushing water.

When I rise to my feet, I feel strangely sated. I can't remember when the plane is due back at the landing strip, but it hardly matters now. Johnny will tell the pilot that there was a terrible calamity and there is no one left alive to search for. No one will ever come looking for me. To the world, I am dead.

I scoop up mud from the river and anoint my face and arms with a fresh layer. Already I feel the sun's heat beating down on my neck and swarms of biting insects rise from the reeds. The day has scarcely begun, and I am already exhausted.

I force myself to my feet. Once again, I trudge south.

BY THE AFTERNOON OF the next day, I am so hungry that I double over with stomach cramps. I drink from the river, hoping that water will ease the pangs, but I gulp down too much, too fast, and it all comes up again. I kneel in the mud, retching, weeping. How easy it would be to give up now! To lie down and let the animals take me. My flesh, my bones, will be devoured by the wilderness, forever joined to Africa. From this land we all arose, and to this land I return. It is a fitting place to die.

Something splashes in the water, and I lift my head to see two ears flicking on the surface. A hippo. I'm close enough to alarm it, but I'm beyond fear, beyond caring if I live or die. Though it knows I'm here, it continues to bask unconcerned. The murky water ripples with small fish and insects, and cranes splash down from the sky. In this place where I am dying, there is so much life. I watch an insect flutter toward a thicket of papyrus reeds, and suddenly I'm hungry enough to eat even that dragonfly. But I'm not fast enough, and all I catch is a handful of reeds, thick and fibrous. I don't know if they'll poison me; I don't care. I just want something to fill my stomach and ease the cramps.

With the pocketknife from my knapsack, I slash a handful of reeds and bite down on the stems. The rind is soft, the flesh starchy. I chew and chew until all that's left in my mouth is a hard wad of fibers, which I spit out. My cramps are easing. I cut another handful of papyrus reeds and gnaw on them, like an animal. Like the hippo, who calmly grazes nearby. Slash and chew, slash and chew. With every mouthful, I take the bush into me, feel it become one with me.

The woman I once was, Millie Jacobson, has reached the end of her journey. On my knees, at the river's edge, I surrender her soul.

BOSTON.

MAURA COULD NOT SEE HIM, BUT SHE KNEW HE WAS WATCHING HER.

"There, up on the ledge," said Dr. Alan Rhodes, the zoo's large-cat specialist. "He's just behind that clump of gra.s.s. He's hard to make out because he blends so perfectly into the rocks."

Only then did Maura spot the tawny eyes. They were fixed on her and only her, with the cold, laser focus that binds predator to prey. "I would have missed him completely," she murmured. Already shivering in the cold wind, she felt her chill deepen as she met the cougar's unrelenting stare.

"He didn't miss you," said Rhodes. "He's probably been tracking you since we walked around that bend, into his field of view."

"You say he's tracking me. But not you?"

"For a predator, it's all about identifying the most accessible prey, the easiest one to bring down. Before he'd attack a full-grown man, a cougar will choose a child or a woman. Look, do you see that family coming toward us? Watch what the cougar does. Watch his eyes."

Up on the ledge, the cougar's head suddenly swiveled and he snapped to full alertness, his muscles rippling as he rose to a crouch. His gaze was no longer on Maura; instead those laser eyes were fixed on a new target, which was now scampering toward his enclosure. A child.

"It's both movement and size that attract him," said Rhodes. "When a kid goes running by this enclosure, it's like flipping a switch inside a cat's head. Instinct takes over." Rhodes turned to her. "I'm curious why you're suddenly interested in cougars. Not that I mind answering questions," he added quickly. "In fact, I'd be happy to tell you a lot more over lunch sometime, if you'd like."

"I find big cats fascinating, but I'm actually here because of a case we're working on."

"So it's about work."

Was that disappointment she heard in his voice? She couldn't read his face, because he'd turned toward the enclosure, his elbows propped on the guardrail, his gaze back on the cougar. She considered what it might be like to have lunch with Alan Rhodes. Interesting conversation with a man who was clearly pa.s.sionate about his work. She saw intelligence in his eyes, and although he wasn't particularly tall, his work outdoors kept him tanned and fit. This was the solid, reliable sort of man she should have fallen in love with, but the spark wasn't there. Chasing that d.a.m.n spark had brought her nothing but sorrow; why did it never ignite with a man who could make her happy?

"How does cougar behavior relate to an ME's case?" he asked.

"I want to know more about their hunting patterns. How they kill."

He frowned at her. "Has there been a cougar attack in the state? That would certainly support the rumors I've been hearing."

"What rumors?"

"About cougars in Ma.s.sachusetts. There are reported sightings throughout New England, but right now they're the equivalent of ghosts, sighted but never confirmed. Except for the one killed in Connecticut a few years ago."

"Connecticut? Was he an escaped pet?"

"No, that animal was definitely wild. It was. .h.i.t by an SUV on a highway in Milford. According to DNA a.n.a.lysis, he migrated here from a wild cougar group in South Dakota. So these cats have definitely made it to the East Coast. They're probably right here, in Ma.s.sachusetts."

"I find that scary. But you sound almost thrilled by the prospect."

He gave a sheepish laugh. "Shark experts love sharks. Dinosaur guys are nuts about tyrannosaurs. It doesn't mean they want to run into one, but we all share that sense of wonder about big predators. You know, cougars used to own this continent, coast to coast, before we chased them out. I think it's pretty exciting that they're coming back."

The family with the child had left the exhibit and moved on down the zoo path. Once again the cougar's gaze turned to Maura. "If they're here in the state," she said, "there goes any thought of a peaceful walk in the woods."

"I wouldn't get freaked out about it. Look how many cougars there are in California. Night-motion cameras have caught them wandering around in LA's Griffith Park. It's rare that you hear about an incident, although they have attacked joggers and bicyclists. They're primed to chase fleeing prey, so movement catches their eye."

"Then we should stand and face them? Fight back?"

"To be honest, you'd never see one coming. By the time you're aware he's there, he's already sinking his jaws in your neck."

"Like Debbie Lopez."

Rhodes paused. Said quietly: "Yes. Like poor Debbie." He looked at her. "So has there been a cougar attack here?"

"It's a case from Nevada. The Sierras."

"These cats are definitely there. What were the circ.u.mstances?"

"The victim was a female backpacker. Her body had been scavenged by birdlife by the time she was found, but several details made the ME consider cougar attack. First, the victim was disemboweled."

"A not-infrequent finding in a large-cat kill."

"The other thing that puzzled the ME was where the body was found. It was up in a tree."

He stared at her. "A tree?"

"She was draped over a branch about ten feet above the ground. The question is, how did she get up there? Could a cougar have dragged her?"

He thought about this for a moment. "It's not cla.s.sic cougar behavior."

"After the leopard killed Debbie Lopez, he dragged her up onto the ledge. You said he did it out of instinct, to protect his kill."

"Yes, that behavior's typical of an African leopard. In the bush, they face compet.i.tion from other large carnivores-lions, hyenas, crocodiles. Hauling a large kill up a tree is how they keep it away from scavengers. Once the kill is safely cached in the branches, the leopard can feed at its leisure. In Africa, when you see a dead impala up in a tree, there's only one animal who could have put it there."

"What about cougars? Do they use trees?"

"The North American cougar doesn't face the same scavenger compet.i.tion that carnivores do in Africa. A cougar might haul prey into heavy brush or into a cave before feeding. But drag it up a tree?" He shook his head. "It would be unusual. That's more like African leopard behavior."

She turned toward the enclosure again. The cat's eyes were still riveted on her, as if only she could satisfy his hunger. "Tell me more about leopards," she said softly.

"I highly doubt there's a leopard running around in Nevada, unless it escaped from some zoo."

"Still, I'd like to know more about them. Their habits. Their hunting patterns."

"Well, I'm most familiar with Panthera pardus, the African leopard. There are also a number of subspecies-Panthera orientalis, Panthera fusca, Panthera pardus j.a.ponensis-but they're not so well studied. Before we hunted them nearly to extinction, you could find leopards across Asia, Africa, even as far west as England. It's sad to see how few of them are left in the world. Especially since we owe them a debt for boosting us up the evolutionary ladder."

"How did they do that?"

"There's this theory that early hominids in Africa fed themselves not by hunting, but by stealing meat that leopards had stored in trees. It would have been the equivalent of a fast-food outlet. No need to chase down an impala yourself. Just wait for the leopard to make the kill and drag it up a tree. He'll eat his fill and leave for a few hours. That's when you s.n.a.t.c.h the rest of the carca.s.s. That ready supply of protein might have boosted the brainpower of our ancestors."

"The leopard wouldn't stop you?"

"Radio collar monitoring confirms that leopards don't stay with their kills during the day. They'll gorge, leave for a while, then return hours later to feed again. Since the carca.s.ses are often disemboweled, the meat stays good for a few days. It gave us hominids a chance to sneak in and steal dinner. But you're right, it wouldn't have been a risk-free proposition. You find plenty of prehistoric hominid bones in ancient leopard caves. While we were stealing their dinner, they sometimes made us theirs."

She thought of the cat in her own home, and how it watched her as intently as this cougar was doing now. The connection between felines and humans was more complex than between mere predator and prey. A house cat might sit in your lap and eat from your hand, but it still had the instincts of a hunter.

As do we.

"They're solitary animals?" she asked.

"Yes, like most felids. Lions are the exception. Leopards in particular are solitary. Females leave their cubs alone for periods up to a week, because they prefer to hunt and forage by themselves. By a year and a half, those cubs have left Mom and they're off to establish their own home range. Except when they breed, they keep to themselves. Very secretive, very hard to spot. They're nocturnal hunters with a reputation for stealth, so you can see why they held such a powerful place in mythology. It would have made the darkness terrifying for ancient man, knowing that, on any given night, you might find a leopard's jaws clamped around your throat."

She thought of Debra Lopez, for whom that terror would have been the last thing she registered. She glanced toward the leopard enclosure just a few yards away. Since the zookeeper's death, a temporary screen had been erected to hide the cage, but two zoo visitors stood there now, snapping cell phone photos. Death was a rock star who always drew an audience.

"You said big cats disembowel their kills," she said.

"It's just a consequence of how they feed. Leopards will rip open the body cavity from the rear. That releases the entrails, which they'll consume within the first twenty-four hours. It keeps the meat from decaying too quickly, so the cat can take its time feeding." He paused as his cell phone rang. With an apologetic look, he answered the call. "h.e.l.lo? Oh G.o.d, Marcy, I completely forgot about it. I'll be right there." He hung up with a sigh. "Sorry, but they're expecting me at a board meeting. It's the eternal hunt for funds."

"Thank you for seeing me. You've been a big help."

"Anytime." He started down the path, then turned and called: "If you ever want a private after-hours tour, let me know!"

She watched him hurry away around the bend, and suddenly she was alone, shivering in the wind.

No, not entirely alone. Through the bars of the empty leopard's cage, she glimpsed blond hair, tawny as a lion's mane, and broad shoulders clad in a brown fleece jacket. It was the zoo's veterinarian, Dr. Oberlin. For a moment they eyed each other like two wary creatures who have unexpectedly come face-to-face in the bush. Then he gave a brusque nod, a wave, and vanished back into the camouflaging shrubbery.

As invisible as a cougar, she thought. I never even knew he was there.

"IF INDEED THESE VARIOUS ATTACKS IN DIFFERENT STATES ARE LINKED, then we're dealing with a set of highly complex ritual behaviors," said Dr. Lawrence Zucker. A criminal psychologist who served as consultant to Boston PD, Zucker's pale, hulking figure was a familiar sight in the homicide unit. From his seat at the head of the table, he eyed Maura and the four detectives who'd gathered in the conference room that morning. There was something disturbingly reptilian about Zucker, and as his gaze swept past Maura, it felt like the cold flick of a lizard's tongue on her face.

"Before we get ahead of ourselves," said Detective Crowe, "we haven't yet established that these attacks are linked. Dr. Isles came up with that theory, not us."

"And we're still digging into it," said Jane. "Frost and I drove up to Maine yesterday to look into the case that happened five years ago. A victim named Brandon Tyrone, who was found gutted and hanging from a tree."

"And what do you think?" asked Zucker.

"I can't say the picture's any clearer. Maine State Police are focused on only one suspect, a man named Nick Thibodeau. He and the victim knew each other. They may have had a falling-out, which triggered the killing."

Crowe said, "I called Montana and Nevada, spoke to detectives about their cases. They believe cougar attacks could explain both incidents. I don't see how the out-of-state cases connect to ours, or to the homicide in Maine."

"It's the symbolism that connects them all," said Maura, unable to hold her silence. Neither a cop nor a psychologist, she was once again the intruder at this meeting, and had come at the invitation of Dr. Zucker. As they all turned to look at her, she felt the wall of skepticism looming in her way. A wall she'd have to batter down. Crowe had all force fields up. Both Frost and Jane were trying to look open-minded, but she'd heard the lack of enthusiasm in Jane's voice. As for Johnny Tam, he remained as opaque as ever, keeping his opinions to himself.

"After I spoke to Dr. Rhodes about leopard biology, I realized that was the common thread. The way a leopard hunts, the way it feeds, the way it elevates its kill. We see it in all these victims."

"So who are we looking for?" Crowe sn.i.g.g.e.red. "Leopard Man?"

"You make light of it, Detective Crowe," said Zucker. "But don't dismiss Dr. Isles's theory out of hand. When she called me about this yesterday, I was doubtful, too. Then I reviewed those out-of-state homicides."

"Nevada and Montana weren't necessarily homicides," Crowe pointed out. "Again, the ME's say those could have been cougar attacks."

"Dr. Rhodes said cougars don't normally drag their kills into trees," said Maura. "And what happened to the other members of both parties? There were four backpackers in the Nevada group. Only one was found. There were three hunters in Montana, and the remains of only two were found. Cougars couldn't have wiped them all out."

"Maybe a family of cougars."

"It wasn't a cougar at all," said Maura.

"You know, Dr. Isles, I'm having a little trouble keeping up with all your changing theories." Crowe looked around the table. "First, we hear this killer hates hunters and that's why he hangs and guts them. Now it's, what? Some crazy guy who thinks he's a leopard?"