Except for this school group and two elderly women up ahead of us who were examining the old stone lantern that was lit every year at the opening of the cherry blossom festival, I still hadn't seen anyone who looked remotely interested in Kevin and me.

"Where were you?"

"Walking through the cloisters on my way back to the residence. It was about nine o'clock at night," he said. "Same thing, I heard someone following me. This time one of the seminarians showed up, so I said, 'Come on, let's go after this guy.' Except he said, 'What guy?' And the next thing I knew, whoever was there took off running toward the lower garden." He sounded disgusted. "By the time I reached the top of the stairs, he'd vanished into the woods. I'm sure he left the grounds through the path by the outdoor Stations of the Cross. From there it's easy to disappear into the neighborhood on Quincy Street."

"Kevin, you ought to tell someone about this. I mean, besides me."

"Come on, Soph. What am I going to say? I have no witnesses."

"What about the seminarian who was there? He must have heard something."

"Nope. Paul said he didn't see or hear a thing. Same as the knight who checked out the crypt." He sighed. "Forget about it. Let's talk about your project."

"Kevin-"

"The reason we're here freezing our b.u.t.ts off is that you wanted to talk to me about that book of cherry blossom photos you want to put together, right?"

"Yes, but-"

"So tell me."

He was done talking about his stalker. "It's a fund-raiser for the Adams Morgan Children's Center," I said. "I could use your help."

"Cherry blossom photo books have been done already. A lot."

"This wouldn't be lots of pictures of pink clouds of blossoms wreathing the monuments. I'm talking about photos of the trees like they are today when it's gray and miserable, or in the fall, or covered with snow. And not just the Tidal Basin, but the out-of-the-way places people don't usually think about, like Meridian Hill Park, Scott Circle, Stanton Park." He shook his head. "Come on, Kevin, I think it's a good idea. But I need your help identifying all the different varieties of cherry trees and which ones are planted where."

He pulled down a branch filled with cl.u.s.ters of tightly furled buds from over our heads. "These are Yoshinos, the most common cherry tree in D.C., prunus x yedoensis. It's a hybrid. They're the trees with the light pink flowers, very fragrant. When they're in bloom they look like your pink clouds." He released the branch. "Choose another subject, Soph."

A pair of ducks landed in the Tidal Basin and swam under the protection of a low-hanging branch in front of us.

"Such as?"

"Photograph Washington's unknown-or little-known-gardens. I can show you where they are and introduce you to the people who care for them. Everyone thinks they know D.C., but there are loads of beautiful gardens in this town that have either been forgotten or people look at them every day but don't see them anymore. Photograph the places that are hiding in plain sight, so to speak."

I was surprised by the pa.s.sion in his voice, but maybe he was right: Find the gardens that had become invisible for one reason or another in this city of gardens and show people what was right under their noses.

He reached inside his habit and pulled out a white business envelope as another gust of wind tugged at his long robe. "I brought this for you. It's an article I wrote a few years ago on some of the gardens I think you might want to look at."

"Thank you." I opened the envelope and scanned his list. "It's a good idea, Kevin. Maybe I could talk you into collaborating, since you already know so much about these gardens?"

"I'll be glad to help, but if you want to sell books for charity, leave my name out of it. I have a reputation for riling people up."

I slipped the article into my camera bag. "I'll take my chances."

"Come on," he said. "Those ladies have finished examining the stone lantern. Let's walk over there. I'd like to look at the old markings. You know it once belonged to a shogun, don't you? It's one of a pair."

"No, I didn't know." I linked my arm through his as we started up the hill. "Do you think whoever is following you might be someone you've riled up? A person who doesn't like your views on climate change or the environment?"

He hesitated a moment too long before he said, "No. I don't think so."

I knew then that he hadn't told me everything about his stalker. "You have an idea who it is, don't you?"

"That's not true. I don't know who it is."

He wasn't going to make this easy. "All right, you don't know who, but you do know why someone's following you." When he didn't reply, I said, "What's going on, Kevin?"

We reached the old lantern. "I don't want to get you in the middle of anything."

"Nice try. We've known each other too long."

A muscle flexed in his jaw as he traced the worn outline of a crescent moon on the old stone with his finger. I waited. Logic dictated that he would tell one of his brother friars, men he should trust implicitly to keep secrets. Instead I had a feeling he was going to unburden himself to me.

Finally he said, "Back in February when I was in London to speak at a conference at Kew Gardens, I came across something quite by accident. When I got home I did some more investigating. If I found what I think it is, this whole thing could be pretty big."

"What thing? And define pretty big."

"Potentially millions of dollars, maybe a lot more. It's complicated. I can't tell you anything else until I'm sure I'm right. There's one more piece of the puzzle I still need to put together."

The Franciscans were a mendicant order and took vows of chast.i.ty, poverty, and obedience symbolized by the three knots on Kevin's cincture. They lived a simple life with few possessions. Kevin had given all of his royalties and any money he earned from the publication of his book to the Franciscans, supporting their mission in the Holy Land and helping charities that worked for the poor and the disabled.

Whatever Kevin had discovered, the money would go to those same causes, not his own personal wealth.

"Good G.o.d, what is it?"

"I've said enough. Like I told you, it's a huge long shot. I'm not sure I'm right."

"Of course you are. Otherwise why would someone be stalking you?"

He gave me a long, steady look. "No one knows better than you, Sophie, because you're married to a guy who used to be a covert CIA officer, that a person can't talk about what he doesn't know. So can we just leave it at that?"

Nick Canning, my husband, had been with the CIA for years until his cover was blown last fall. The story had been in the press everywhere, and that ended his clandestine career. Kevin was right. You don't have to lie when you don't know the truth.

"At the party last night, Thea Stavros said she heard rumors about a project you were working on," I said. "Do you think she knows?"

He traced more markings on the lantern before he answered, and he seemed uneasy. "I've had to ask a few people for some information, including Thea, but I'm sure she doesn't know or hasn't figured anything out. The project she was talking about last night was the history book on colonial gardening."

"Does your missing puzzle piece have something to do with that book?"

He pressed his lips together and shook his head. "I've said enough."

"That sounds like a yes. Come on, Kevin, you trusted me enough to tell me someone's been following you."

A long look pa.s.sed between us, and I knew he needed to tell someone.

"All right," he said at last, "but you can't say a word to anyone. I'm serious."

I crossed my heart with a finger. "Hope to die."

He took a deep breath. "If I'm right, I found something of historical importance that n.o.body seems to have realized is out there, even though it's probably been hiding in plain sight. Like I said, it could be worth a lot of money to the right people. I want to be the person who makes that discovery, solves the puzzle. And be the first to write about it."

At least now I understood the thinking behind his idea for my garden book, since it mirrored his own project: photograph the city's jilted beauties, gardens that were overlooked and ignored. In other words, hiding in plain sight.

"So the reason for all the secrecy is that you don't want someone stealing your story?"

He nodded. "I don't own the information I uncovered. It's in the public domain, and anyone who figured out what I was doing could obtain the same doc.u.ments. So far no one else has. Right now, it's my treasure hunt."

"Was that why you were arguing with Edward Jaine?"

He gave me a severe look. "In a word; no. That was about something else."

"What did you retrieve from the catacombs?"

He made a zipping motion across his lips.

"Kevin, someone knows something or he wouldn't be following you."

"I know. That's what's bothering me. I don't know who it could be."

"What are you going to do?"

He shrugged, but he still looked worried. "What can I do? Keep searching and watch my back."

"You'd better be careful."

"Whatever happens is in G.o.d's hands." He glanced at his watch. "Sorry, Soph, but I ought to go. I promised Thea I'd stop by the library and take a look at those books she was telling me about last night." He grimaced. "Then I'm meeting someone for coffee."

"You don't look too happy about it."

"I have to say something I wish I didn't have to say."

"Then why are you doing it?"

"If I don't, more people are going to get hurt later. And I'll know I could have done something to prevent it. It's better to get this over with." He sighed and pulled his car keys out of a pocket inside his robe. "Are you leaving now, too?"

"I think I'll stick around and take some more pictures. I have a meeting at the Smithsonian, but it's not for an hour."

"Another job?"

I nodded. "An editor from Museum Press hired me to take the photographs for a history book on the National Mall. So I'll see her, and then at the end of the day I'm meeting Ursula and Yasmin at the monastery. She wants to walk through the church and the garden. Again."

"I remember." He made a face. "The kids from Brookland Elementary are coming over at two to clean up the beds in their vegetable garden. We'll be long gone when you do your walk-through with Ursula."

"That school garden is such a great community project."

"Especially when they get to eat what they've grown and realize food doesn't only come from a can or a package." He leaned over and kissed me on the cheek. "If you ever want to take photographs, you're welcome to come by. We could put them on the garden website, get some publicity. You know we're always looking for donations."

"I'd be happy to, but you'd need written permission from every parent," I said. "A friend who works for the Post accidentally took a picture for a school story without knowing one of the kids was in the witness protection program. It was a mess."

His eyes widened. "I'll keep that in mind."

"I can take garden pictures without the kids," I said. "You can put those on your website. I'll come by early and check it out."

"That would be great, though there's not much to check out right now. Too early in the season." He gave me a swift hug and left, robes flying as he strode down the promenade. As he disappeared up the steps by the FDR Memorial, my foot kicked something on the ground. A key.

The head was dark gray molded plastic, the same color as the lantern. I picked it up. On one side, the number 58 was etched into the plastic. It was too small and oddly sized to be a house key or a key to a room at the monastery; it looked more like it belonged to a storage locker or a trunk.

Kevin must have dropped it when he pulled out his car keys, or maybe when he pa.s.sed me the envelope, unless one of the two women who'd just been here had lost it. I shoved it in my jeans pocket. When I went over to the monastery later today, I'd ask him if it was his.

I took pictures for another half hour and thought about my conversation with Kevin. Had he moved whatever he'd hidden in the catacombs to a new, safe place? I hit the Unlock b.u.t.ton for my car door and wondered what the little gray key might open.

More than that, I wondered what object could be so precious to a Franciscan friar that he went to such lengths to keep it hidden, especially when he lived in a house whose only other residents were religious men of G.o.d.

3.

A parking s.p.a.ce opened up across the street from the old-fashioned carousel on the Mall as I drove up. In two weeks, the flowering cherries, dogwoods, magnolias, and redbud would begin to bloom, and Washington would be at its loveliest, bringing tens of thousands of tourists in buses and cars that choked the Mall and overran the monuments and museums. But today the city still belonged to the locals. I liked it without the crowds, days when you could get a parking place practically in front of the Smithsonian Castle, and the museums and art galleries were so empty you might have an entire room filled with centuries of culture or the world's greatest paintings practically to yourself.

Nearly eight months ago, my husband and I moved here after living in London for twelve years. Nick's career as a covert operative with the CIA had ended after a nerve-racking, harrowing time when he had been on the run for three months and I had returned to Washington to be near family and friends. It hadn't been an easy decision to leave a city we both loved, but we knew if we stayed in England any longer, we'd be expats forever and maybe strangers to each other because we were together so seldom.

Living with a spy is not easy. I had never been able to tell anyone this, not even my family, who had known Nick only as a geophysicist working for a British oil and gas exploration company that had been drilling for oil in Russia. I knew what Nick really did before the wedding, and I liked to think I wasn't nave about what his clandestine life would mean for us. I'd grown up around Washington where everyone knew more spooks than they realized. What I didn't understand was how hard it would be to live with someone you could never truly know, who erected impenetrable walls and spun webs of fict.i.tious truths without batting an eye, who could compartmentalize his life with what seemed like ruthless efficiency.

Then Nick's cover was blown and he was PNG'd-declared persona non grata-by the Russian government. But after being in the field for so long, he didn't want to return to a desk job in Langley. Three and a half months ago, after a couple of bottles of champagne on New Year's Eve and a discussion that lasted until dawn, Nick handed in his resignation to the CIA and I left the small photography studio where I'd worked for the past six months. I picked up freelance a.s.signments right away-almost more work than I could handle-but it wasn't so easy for Nick, who got in touch with friends and started calling in favors for job leads at meetings or lunches or over drinks.

Anyone who has been recruited as an informant by a foreign country's intelligence agency can bend over and kiss his a.s.s goodbye if he's ever outed, because professionally no one will trust you again. You're a snitch and you can be bought. It's different if you were hired by the CIA, as Nick was, and had gone through Agency training, because intelligence gathering is your job. You have a regular paycheck, a pension, health insurance, and an annual vacation, and you have sworn an oath of loyalty to your country. But it's still a complicated and fickle world when you leave the life to start over again on the outside. Whatever Nick did next would have to be something unusual, almost certainly not advertised on any website or with a written, well-defined job description.

In the beginning of February, he came home one day and told me Quillen Russell was forming a consulting firm and had asked Nick if he wanted the position as his energy expert. Washington needs more consulting firms like the beach needs more sand, but Quill had been secretary of state in a previous administration and he was G.o.dfather to the oldest daughter of the current president. I doubted they would be advertising for clients, and the new office was going to be within walking distance of the White House.

"What will you do?" I asked Nick.

He gave me a dangerous half smile and said, "Whatever they ask me to do."

"It'll be like the Agency again, won't it?"

"Not really. Quill sees it more as being fixers or facilitators for problems or situations that are . . . unconventional."

"Your fee won't be a line item in someone's budget?"

He laughed and pulled me into his arms. "Do you mind if I go away for a while?"

"Yes, I do," I said as he kissed my hair. "I was just getting used to having you home after all the time you spent in Russia."