I knew the way to the back corridor and I remembered where Thea had found Kevin's doc.u.ments on that bookcase. The corridor was deserted, so no one saw me pull the bundle of papers off the shelf. Kevin had requested three doc.u.ments: a historic buildings survey written by someone at the National Park Service: The L'Enfant-McMillan Plan for Washington, D.C., a dissertation on Pierre L'Enfant's vision for Washington, and finally a report from 1909 presented to the Columbia Historical Society: The Re-Interment of Major Pierre Charles L'Enfant.

I stared at the last report. Pierre L'Enfant had been reburied at Arlington? I tried to remember the year he died from what I'd read in "No Little Plans"-sometime in the early 1800s-but I could look that up later. I skimmed the report. It was just over twenty pages, written in flowery, effusive language describing L'Enfant's genius and patriotism, along with a detailed account of his body being exhumed from "a lonely and unmarked grave" in Green Hill, Maryland, in 1909 after Congress granted the sum of one thousand dollars to bury him in a more fitting tribute at Arlington National Cemetery. From Maryland, his body had been moved to a vault in Mount Olivet Cemetery in Washington before it was carried to the Capitol, where he lay in state in the Rotunda. Finally, he was buried with full honors on a bluff overlooking the city of Washington.

At the end of the hall, a door to one of the study rooms opened and a man walked out. I shoved the papers back on the shelf and left. The last thing I wanted to do was get Logan sacked. And thanks to her, giant pieces of the puzzle were slamming into place in my head.

Kevin had been looking into L'Enfant's burial at Arlington as well as the McMillan Plan, plus he connected Senator Francis P. Quincy, a descendant of Francis Pembroke, with Charles Moore, the secretary of the commission that had drafted that plan. I wasn't entirely sure why, but I knew someone who would be able to answer my questions.

The guard in the lobby of the Adams Building lobby checked my bag as I left. I walked outside and called Olivia Upshaw, who answered right away.

"It's Sophie Medina," I said. "I'm at the Library of Congress. I've been doing some extra research on Pierre L'Enfant and I've got a couple of questions. I was wondering if I could drop by and talk to you."

"Sure." She sounded pleased and a bit surprised at my industriousness. "I'm at an all-day affiliates conference downstairs in the west wing of the Castle. How about tomorrow, say ten o'clock?"

"I'd really like to do this today. Do you have a coffee break or a lunch break? It won't take long, I promise."

"We just started a break. We go back in half an hour."

"I can be there in fifteen minutes."

"This must be really important."

"It is."

"Meet me at the information desk in the Great Hall."

"I'll be there," I said. "Thank you."

The sudden burst of warm weather three days before the first day of spring had brought out the tourists in droves. Unlike last week, the Great Hall of the Smithsonian Castle was jammed with people milling around the gift shop and filling the tables of a cafe across from the information desk. Olivia wasn't there when I arrived, nor did I see her in the crowded room.

"Are you Sophie?" A woman standing behind the information desk came over to me. "Olivia asked me to tell you that she had to take a call but she'll be here in just a moment."

"Thank you."

I looked through the rack of museum brochures and tourist information while I waited. A pink-and-white pamphlet decorated with cherry blossoms listed spring events at the Mall museums. I picked it up because one exhibition caught my eye: the exquisite blown-gla.s.s sculptures of Dale Chihuly at the Hirshhorn.

"Sophie? Sorry I was detained."

Olivia stood there, dressed in a black pantsuit and white blouse, stiletto heels, juggling a tablet computer, a phone, and a pack of tissues. She set the electronics on the information desk and reached around with a hand to flip her long blond hair so it fell over one shoulder. Then she blew her nose.

"Are you all right?" I asked.

She gave me a miserable look. "Allergies. Tree pollen. What can I do for you?"

"I was wondering if you could answer a question. Can you tell me whether the decision to rebury Pierre L'Enfant at Arlington Cemetery had anything to do with the McMillan Plan?"

"That's what you want to know?"

I nodded.

"Strictly speaking, no, it didn't."

"Are you sure?"

"Of course I'm sure. L'Enfant was buried at Arlington because of a friendship between Teddy Roosevelt and the French amba.s.sador, a man named Jules Jusserand. Jusserand wanted L'Enfant up there in the pantheon of French heroes who helped the Americans during the Revolutionary War just like the Marquis de Lafayette. So he became a huge L'Enfant promoter and eventually, in 1908, I believe it was, Congress approved money to move the grave, and the secretary of war approved the site in Arlington where he's buried today."

"And this had nothing to do with the McMillan Plan?"

She sneezed and blew her nose again, giving me a pointed look. "Well, since you read the ma.n.u.script of 'No Little Plans'-"

"I did."

"Then you know the McMillan Commission essentially rehabilitated L'Enfant a century after George Washington dismissed him."

"Okay," I said. "Have you ever heard of Senator Francis P. Quincy? Probably Francis Pembroke Quincy? He knew Charles Moore and he might have been involved with the McMillan Commission, even though he wasn't a member."

She picked up her tablet computer. "No, but I'll check our database." After a moment she said, "Sorry. No connection between the two."

"Nothing?"

She continued typing and said, without looking up, "Charles Moore kept extensive sc.r.a.pbooks of correspondence and news clippings, plus his diaries, but I don't find anything linking him to Senator Quincy. Later Moore became head of the Ma.n.u.script Division of the Library of Congress and was responsible for bringing L'Enfant's original 1791 design for Washington to the library so it could be preserved . . ." She kept reading. "This just goes on about Moore . . . No, there's nothing."

"Olivia. You're needed in the Commons. We're about to begin the next presentation." A dark-haired woman wearing a black suit and white blouse like Olivia had joined us.

"I'll be right there."

"Thanks for the help," I said.

"No problem. I'll be in my office tomorrow. The conference goes on for a couple of days, but I only need to be here today. I'll e-mail you and we can figure out a time to get together to go over your photos now that you've read the ma.n.u.script."

I nodded. "What's this conference about? Thea Stavros from the Library of Congress and Ryan Velis from Monticello are here, too. Are all of you together?"

She seemed surprised that I knew about Thea and Ryan, but she said, "Oh, yes, the gang's all here. The subject is social networking and new media for museums, historical sites, public gardens, cultural inst.i.tutions. Places that rely on donations to keep their doors open." She picked up her tablet and phone and stuffed the tissue packet into a pocket. "They're teaching us all the latest tricks to stay relevant in the digital age . . . I'd better go. See you, Sophie."

I was halfway to the mall exit when Thea Stavros called my name. I looked up as she came down the staff-only staircase next to the room containing the crypt of James Smithson, the Smithsonian's benefactor.

"What are you doing here?" she asked.

"Just leaving," I said. "I had a quick meeting with an editor I'm working with at Museum Press."

"How was London? Did you learn anything more about Kevin's book and what he was looking for?"

"How did you know I went to London?"

She smiled. "Ryan Velis told me. He also said he contacted Zara Remington at the Chelsea Physic Garden on your behalf, so I presumed you went there because of Kevin."

"I went with my stepfather," I said, "sort of a last-minute vacation. I figured as long as I was going, I'd stop by the garden."

The last time we spoke, I'd told Thea about the book, but I hadn't mentioned the Fairbairn letter. At the time I hadn't realized its significance and I hadn't yet met Ryan, who'd told me about the seeds. So Thea didn't know about them, either.

Unless Ryan had told her.

Both Thea and Ryan had been Kevin's colleagues, people he trusted. I still thought whoever killed him had known him well, and Bram said a woman had come into the gallery with my paperwork and left with the book.

Thea was still waiting for my answer to her question about whether I had learned anything more about Kevin's book and what he was looking for when I was in London. My instincts told me she was on my side.

"The book is gone, Thea," I said. "A woman walked into Asquith's with doc.u.ments she got from my apartment and persuaded someone who worked there that I wanted the book back."

The horrified expression on her face confirmed it: She hadn't known until now that it was missing. "Dear G.o.d," she said, "how in the world did that happen?"

"Asquith's is working with the police," I said. "Bram is devastated. Only a few people knew he had the book in their safe."

"I will be utterly heartbroken if that book disappears forever. It should be exhibited in a place like the Library of Congress, where it can be enjoyed and appreciated, not locked up in someone's safe-deposit box forever because the owner can't display a stolen treasure." She walked down the remaining stairs and joined me. "Ryan called me after you left Monticello, and we had quite a conversation. I've been combing through our records at the library looking for any additional reference to the seeds Thomas Jefferson might have kept in the White House."

"I see."

"And what about you? Did you turn up anything new in London?"

I told her then what I learned about Kevin's sister and that I believed it had given him an even stronger motive for finding the seeds.

"The poor man. How perfectly awful for him. Kevin may have been a scientist, but he did believe in miracles and the power of prayer."

"He apparently contacted a number of pharmaceutical companies, looking for trial studies of Alzheimer's drugs that might be suitable for her."

"I wonder if he also mentioned the seeds and that he was searching for them. Obviously they could be worth a fortune commercially, to say nothing of the historical value," she said. "Do you think Kevin figured out where they were before he died?"

"I don't know. The last thing he was looking into was the McMillan Commission's plan to resurrect Pierre L'Enfant's original design for the Mall," I said. "Do you think the seeds could be somewhere here? I mean, on the Mall?"

She looked stunned. "My G.o.d, wouldn't that be something? But where would they be? There's no monument to L'Enfant, and if they're in the cornerstone of, say, this building or the Arts and Industries Building next door, then good luck retrieving them."

"There is a monument to Pierre L'Enfant," I said. "His grave overlooking Washington."

"Yes, but surely you know what it looks like? A ma.s.sive stone table set on a pedestal. It would take an act of Congress to get that moved. An act of G.o.d would be easier. If the seeds are there, it's forever."

"In other words, maybe Kevin nearly found them, but they'll stay where they were buried?"

"You'd have to have incontrovertible proof. You're talking about the National Mall or Arlington Cemetery. You don't just stick a shovel in the dirt and start digging." She laid a hand on my arm. "Let me know if you find anything and I'll do what I can to help."

"Thank you. I should let you get back to the conference."

She waved a hand. "Oh, I'm already late. I just came from a meeting with Yasmin Gilberti. The next presentation I'm going to attend is David Arista's talk at two."

"David is here?" I asked, and she nodded. "I didn't know Yasmin was in Washington. I thought she was still in London with Victor. His father is very ill."

"She came home because of David's talk and a meeting with the Creativity Council. I'm not sure when she got back. Victor stayed in England."

Maybe Yasmin flew home to tell her mother in person about the decision to postpone the wedding. Thea didn't appear to have any clue about that news, so I said in a neutral voice, "That makes sense. I'd better be going. And thanks for the offer of help."

Thea gave me a sharp-eyed look. "Are you planning to make a tour of the Mall and Arlington Cemetery?"

I nodded. "I think I might."

"Good luck. Just don't take a shovel. The Park Service frowns on people digging up federal property."

I went directly to Arlington. It seemed like the easiest and most logical place to start. The traffic lights were in my favor, so it took only ten minutes to drive around the Lincoln Memorial across Memorial Bridge to the main cemetery gate. Up ahead of me perched on a hill at the highest point of the cemetery, Arlington House and the grave of Major Pierre Charles L'Enfant overlooked the city of Washington.

Once I explained to a woman in the Visitor Center that I was a photographer working on a project with Museum Press, she gave me a map and a pa.s.s for the Vespa so I could drive through the grounds to L'Enfant's grave, instead of making my way up the steep hill on foot. The streets had names like Eisenhower, Roosevelt, Patton, McClellan, Grant, and Pershing, and the winding drive uphill past row after row of white markers was heartbreaking and haunting in its peacefulness. A few cars were parked next to the steps leading to the Eternal Flame. Maybe when I finished what I'd come to do, I would stop on the way down.

I turned on Humphreys Drive and parked in an empty lot. At eleven o'clock on a Thursday morning, the place was deserted. Here the graves were older, and it looked like a proper cemetery, no rows of white markers. But this land had once been part of a large estate, the mansion built by George Washington's adopted son and later the home of his daughter and her husband, Robert E. Lee, before the U.S. government confiscated it when Lee became a commander in the Confederate Army.

I found a more detailed map of the cemetery on my phone and zoomed in. Perhaps the seeds weren't in the grave but somewhere near it around Arlington House. There was an elaborate flower garden next to the mansion and a colonnaded pavilion that the map called the Old Amphitheater and Rostrum, the gathering site for the cemetery before a new, larger pavilion had been built in the 1920s.

But it seemed to me that all these places were too far away from L'Enfant's tomb. I walked around Arlington House to the steep bluff overlooking the Eternal Flame far below and the view across the bridge to the Lincoln Memorial and the two other iconic monuments, both envisioned by L'Enfant: the Washington Monument and the Capitol dome. A blue ribbon of the Potomac River snaked between a broad expanse of green-tinged trees.

As Thea had said, L'Enfant's grave looked like a large table set on a substantial marble base. His map of the city had been engraved into the top slab. If the seeds were under all that marble, they really would remain there forever. A podium-like marker with a time line of L'Enfant's life and another copy of his map set under Plexiglas stood a few feet away from the grave.

I checked it out. At the base of the marker something had been set into the ground, a small metal box like a safe. I knelt and brushed away dirt. There was a keyed lock set flush into the metal surface.

I sat down hard, staring at the little safe, and thought, I've found the seeds.

Hiding in plain sight, just as Kevin had said that last day at the Tidal Basin. They had to be here.

My phone rang. It was Olivia.

"I've got something for you," she said. "A letter from Senator Quincy to Charles Moore dated March 4, 1902. It's just two lines. Shall I read it?"

"Yes, please."

She sneezed and blew her nose. "Sorry. Here's what it says: Please be a.s.sured of my most sincere thanks for your efforts to persuade the members of the McMillan Commission to accept my donation. I trust you will do your utmost to ensure that some day it is most n.o.bly enshrined. Yours, Francis P. Quincy." She sniffled. "That's it."

"Thank you," I said. "It's very helpful."

Francis Quincy had given Charles Moore the White House seeds, and Moore had done what Quincy asked: made sure they were most n.o.bly enshrined.

"Is this something we could incorporate into the book?" she asked.

"Possibly. We'll have to talk about it."

"Excellent. By the way, David Arista told me he could still get you into the Arts and Industries Building this week since you came back early from London. Starting next week they're going to begin fixing the ceiling, so no one will be allowed in. I think you should take those interior photographs tomorrow."

The hair on the back of my neck p.r.i.c.kled. "Did he tell you this today?"

"No, yesterday. I haven't seen him today. But when I do, I'm going to tell him I want my bunny back." She blew her nose.

"Your bunny?"