She traced the ritual scars on his cheek. "That's a good plan, baby. Play them for the fools they are." Though she liked Tango and Desuetuda. It was the new one, Valkiri, she didn't much care for.

"Is it just playing? Listen to the boy breathe. May have a virus, right enough."

Zora fell silent. Pleading illness, her mother always said, was inviting the devil to supper. And, having lost Earth, and her family, and so much else, she sometimes wondered if Mars were enough recompense.

Sekou seemed so fragile. n.o.body wants to outlive her own child.

She slept poorly and woke early.

BUT THE SOLAR flare subsided in the night, and while the radiation count went down, the nomads bustled around packing. Zora had a chance to talk to Desuetuda, when the two were exchanging hydroponic stimulants recipes they didn't want to trust to electronic mail. But Desuetuda, almost an old friend, wasn't the problem. It was Valkiri.

Marcus helped them drag their equipment back to their rover, and when he took his helmet off after returning, Zora could see he was scowling.

"Not much co-operation there," he said. "I don't think that new girl, that Valkiri, will last long with the tribe."

"Where'd she come from?"

"Lunar nomads. Last of her tribe there. Rest gave up, sold themselves to a cheap labor out-sourcer on Earth-you can't live off the land on Luna." He made a small disapproving sound in his throat. "I wish I could talk to this group's tribe chief. The rest of the tribe's rovers went ahead a day. Tango says they hunkered down and rode the storm out with free radical repair drugs."

"A good way to die young."

"But painless. Stupid. And the drugs also reduce their use of consumables by about fifteen percent. Anyway, Valkiri jumped all over me. Implied we were child endangering just to have little ones here, on the pharm. Hoped Sekou would beg us to go back to Earth."

WHEN VISITORS LEAVE, there is always cleaning up to do. Environmental parameters on oxygen and water consumption must be recalibrated to the normal settings. The hab must be tidied. Reports of the visit must be logged in and the balance sheets of consumables must be recalculated so that things will last until enough energy is generated by the solar panels and the nuke.

So Zora didn't notice the anomaly until after fifteen hours.

SHE HAD JUST put on the top segment of her environment suit, ready to recheck the entry airlock, which she always did when there had been visitors, because once Chocko, a nomad from a different tribe, had left so much grit in the airlock that it froze open. When she looked at the detector in the airlock, she almost dropped her helmet.

The radiation warning was going off like gang-busters.

She looked around wildly for Sekou, who was playing quietly in the high-pressure greenhouse. Well, not playing so much as trying out an adult role-he was clumsily transplanting a frostflower.

The sensor for this airlock showed a lot of radiation, an alarming level. Cautiously, terrified, she grabbed a handheld sensor and ran to the airlock of the greenhouse where Sekou was humming to himself and getting his hands dirty.

Thank Mars the shrilling of the alarm didn't crescendo when she moved toward him.

But it didn't get any softer, either. That meant there was a tremendous beacon of deadly radiation coming from some distance, else moving would make it rise or diminish.

Where, where, where?

Think. If she grabbed Sekou, as was her instinct, she'd have to know where to move him, and quickly. Most likely the cooling system of their nuke, the hab's power source, had sprung a leak. She'd heard of such things.

But knowing that didn't help. She closed her eyes to concentrate and, unbidden, an image came to her of a slow trickling of radioactive water seeping into the clean water supply that heated the house.

"Marcus," she called in a shaky, low voice. Then she gave in to instinct, cycled through the airlock between her and Sekou, and scooped him up into her arms.

They had no environment suit for him. He was still growing too fast. But if she couldn't find the source of the leak, she'd have to get him out of the hab, out into the environment.

Marcus appeared beside her, a sudden angel of rescue. Deliberate and measured movements. Competent. She exhaled a breath of grat.i.tude, as he encircled her and Sekou in his arms.

"It's coming from all over," he said, as if he had read her mind. "Hard to know what could cause such a failure."

"There has to be a safe place in the hab," she said reasonably.

"Look," he said, and broadcast his picture of the hab's health and life systems monitor to her wrist com.

"Sekou-"

Sekou had at first been curious at his mother's urgency, but now he looked scared. He knew what radiation was; children had to know the dangers of their environment, and knowing the signs of radiation, though it was a rare hazard, was just as much a part of their early training as learning to heed airlock failure alarms.

"It will be fine," said Marcus, putting his hand on the boy's head. And to Zora: "I'm looking now at all the sensors in the hab. If there's a safe place, I can't find it. I left an evacuation ball in the main entry. Let's go."

SEKOU DIDN'T LIKE the evacuation ball. "Mama, please, it hurts."

"How can the evacuation ball hurt?" She tried not to grit her teeth as she wadded the limp, slick surface around him and tried to force his legs to bend so she could seal it.

"It hurts my stomach when I have to put my knees up like that."

"It will just have to hurt, then!" She tried to pry his left shoe off, then decided he might need shoes-wherever they ended up.

Marcus intervened. "Take a big breath, my man. Big breath. Hold it. Let it out slow. Now, pull your legs into the ball. See?"

Sekou, half enveloped by the flaccid translucent thing so like an egg, nodded through tears. His puckered little face, trying so hard to be brave, stabbed Zora's heart. It occurred to her for the hundredth time that Marcus was just better with children than she was. Marcus winked at Sekou as he pressed the airtight closure shut.

The transparent ball, designed for animal use, had two handles so Zora and Marcus carried it between them. If only one person were there to carry, it would have been rolled, not a pleasant process for the person inside.

"Go ahead," Marcus murmured. "I'll do the minimum shutdown."

"Marcus, I can do it. Sekou wants you."

"Sekou wants both of us. Go, girl. I can do it faster and we'll all be safer."

THE ROVER WAS ready to go, its own nuke always putting out power. She bundled Sekou inside it and fumbled to embrace him through the pliable walls of the ball, finally settling on a clumsy pat on the top of his head.

"Where to go?" Marcus asked.

"I don't know, I don't know. The Centime's pharm is within range, but are they at their winter place?" Zora was shaking from the shock of being jerked out of her comfortable hab and, worst of all, seeing her little boy in fear and pain and danger. She fingertipped their code and got back cold silence, then the Gone Fishing message.

"Strike out for Borealopolis."

"We need somebody to sponsor us there. Even if we have enough credit to buy consumables, we need somebody to vouch for us."

"Call Hesperson." Hesperson sold them small electronics and solar cell tech.

They did so, and explained the radioactivity problem. The image on the screen was wary. Hesperson sighed. "I wish I could tell you what to do. There's a big decontamination mission near Equatorial City-"

"Our rover would take twenty days to get there! And we would run out of consumables first."

"Let me get back to you on this." And Hesperson was gone.

"The Centimes," Zora said. This couldn't be happening. Couldn't, it was a crazy nightmare, and soon she'd wake up. "We'll contact the Centimes at their summer habitat and ask them to let us use their pharm. They can send us codes to unlock it."

Krona Centime's face, on the monitor, looked distracted and her hair was sticking up as if she hadn't combed it in several days. Maybe something had happened during the Centimes' trip to the southern hemisphere to derange her mind. "Yes! Yes, of course. No, wait, I ought to ask Escudo." Without waiting for an answer she logged off.

Marcus was staring at a life-support monitor. Some of the rover's functions ran much better when the sun was in the sky, and it wasn't up very much in Winter-March. Zora pressed his hand, a gesture he could barely appreciate through the thickness of their gloves.

Sekou's voice cut through the silence like a tiny flute. "Those people have a little girl. Could I play with her?"

Zora had forgotten that Sekou had a com with him when she'd scooped him up to evacuate the hab. Now she was glad-it might come in very handy. Especially if they were to become homeless, landless people in a Martian city where they would be forced to sc.r.a.pe or beg for the very oxygen they breathed.

"She won't be there," said Marcus, and patted his head through the thick membrane. "But I'll ask if you can play with some of her toys." The Centimes were known as spendthrifts and were rumored to have a vast store of luxury items and gadgets. Zora hoped they were also generous.

Escudo Centime's dark, strong-jawed face appeared in Zora's monitor. "Help yourself. I sent a command to the entry airlock to let you in. It should recognize your biometrics."

And so, in the cramped rover; confined to their environment suits with Sekou in his rescue bubble, they set off.

CENTIME PHARM WAS almost invisible, most of it underground, its sharp angles softened by sand settled out of the tenuous atmosphere.

"That's it, thank heaven," said Zora.

Marcus said nothing, just drove the rover toward the hab entrance. Zora could read nothing of his expression through his helmet.

Sekou's voice broke the silence. "When can we go home? I want my Croodelly."

The Croodelly was a piece of worn-out shirt Zora had fashioned into a stuffed animal of indeterminate species. She wished once more that they had had time to pack.

More time? They had none at all. She was totting up in her head the costs of decontaminating the hab and discarding everything damaged within.

Their experiments would have to go; the radiation would start mutations and blight even the most vigorous plants and bacteria.

Marcus, reading her mind, said, "Rehabilitation may be possible."

"If it isn't done properly, we'd be in danger. In the end, we'd shorten our lives and our science would be suspect."

"Or it may be impossible. We can't know now. Here's the airlock. Get ready."

Zora waited for Marcus to approach Centime Pharm's outer airlock. It was silly to be afraid of an empty hab, but she thought, irrationally, of creatures, runaways, ghosts, inside.

Marcus opened the rover hatch and slid out. He plodded a few paces from the rover, then turned and looked back, his suit dusty under the low autumn sun. He couldn't have seen her face through her faceplate, but he stood stock still and looked at the two of them, his wife and his son, standing out in the Martian desert. His voice came through the com. "What are you afraid of, Zora?"

"You feel it, too, don't you? I keep thinking there are things on Mars-no, people on Mars- who don't like us. It's so cold out there, and that hab-it seems haunted."

Marcus turned back to the hab and plodded on.

Zora said, "I know it's irrational, but the darkness-we're so far from New Jersey, aren't we?"

Marcus spoke softly, still marching toward the dark hab entrance. "This was a decision we made. Can't unmake it. But for your sake, if I could, I'd change."

"No, love. We're here. We wanted this, both of us. However it turns out, we'll play it as it lays."

But Sekou, she thought. Sekou is the innocent pa.s.senger.

"Mama," he said. His voice sounded near, even though a thick plastic membrane separated him from her.

"Hush," she said. "Papa's trying to get us a place to stay." Sekou couldn't see the readouts. They had enough consumables in the rover to get back to their own hab, but what good did that do? If they went back, they'd fry.

Because she was watching the rover readouts, she didn't notice at first that Marcus had turned and sprinted back toward the rover. Then she heard the shrill alarm relayed through his com.

He pushed through the rover door and sat down facing forward, not looking at her. "Radiation there, too."

She stared at his helmeted face, in shock. Then she laughed, shakily. "What is this, an epidemic?"

"Are you thinking what I'm thinking?" he asked.

"Yeah. Our visitors."

"Could be Hesperson has something for us," he said. He accessed the contact, and Hesperson's a.s.sistant answered the call.

"How could this have happened?" asked the a.s.sistant. "You think your nomad visitors had something to do with it?"

Zora shook her head. "It could be. There was a new woman with them, Valkiri. No last name, of course. She seemed more... fanatical than the rest."

"New? You know some of these people from before?"

"We trade with them," said Marcus. "Chocko, the one we know the best, he wasn't there, but the other three, except for this Valkiri, were..." He hesitated.

"Friends," Zora said.

Hesperson's a.s.sistant looked glum. "So you could be carrying some nanosaboteur or even a big chunk of something radioactive-"

"No, no, the rover has no signs, except of course for the power plant-"

"There could be a problem with your suit sensors. The radioactive contaminants could be traveling with you."

"The rover sensors-"

"The software in your suit sensors could have damaged that." The a.s.sistant smiled a phony, nervous smile into the screen. "Why not just go back to your hab and wait. I'm sure if you contact your corp, they'll have some advice for you."

Zora and Marcus stared at each other. The Corp that owned their contracts was the last ent.i.ty in the world they wanted to contact right now. The Vivocrypt Corp had paid for four intensive years of education on Earth for each of them, equivalent to doctoral degrees, then financed their journey to Mars and bankrolled their hab and pharm.

This was not charity on the part of the Vivocrypt Corp. The microbiology courses they had taken were very specifically oriented to engineering certain useful substances and organisms that could survive only in extreme conditions. The Vivocrypt Corp had very specific uses for these discoveries.

And Zora and Marcus, who had married and started a family with the prospect of living off the corp, had allowed their science to take some twists and turns that didn't lead directly to what the Corp wanted. Because the training they had received on Earth had aroused in each of them a fierce, shared delight in science for science's sake.

The Vivocrypt Corp would not be pleased that the expensive hab and pharm was no longer of any use as a research and development extension of the Corp.

Zora looked down at Sekou, who was rocking back and forth in the rescue bubble hard enough to bang it against the bulkhead of the rover. His face seemed to be just two big eyes. "We can't go back," she whispered.