Had she really spoken? I thought of calling to her, then decided it might be very embarrassing if I had misheard. I hesitated, and trailed along after her at a respectable distance. We sauntered along, past the Monkey House, through the aviary, and finally on out to the car park. I thought for a moment that I had lost her there. She had disappeared. Then I saw that a grey van on the left had its rear doors open, and I walked hesitantly towards it as though intending to walk right past.

“In here.”

The soft call would have been inaudible to someone ten yards away.

The inside was dark. I climbed up the rear step, then moved forwards on my knees onto a pile of carpets or felt matting. The door clicked to behind me. The painted-over windows allowed enough light inside for me to see the shadow of the woman, crouching in front of me. Before I could move she leaned forward, put her arms around me, and laid her head on my chest.

“Leo. Oh, Leo, thank God. I’ve wondered and I’ve prayed.” Even though the voice was muffled against my coat, her accent was unmistakably American. “Thank God. I thought you were in cover, but there was no way of knowing while you were still inside that hospital.”

I pulled myself away, tingling with the smell of a strangely familiar perfume.

“I’m not Leo,” I said, after a second or two.

She stiffened. “Leo, Leo…”

“I’m not Leo. Leo is — was—” I found myself struggling to say it, almost as though I was forcing myself to acknowledge something for the first time. “Leo was killed in an accident.”

My pulse was thumping again, up around a hundred and forty. Sir Westcott would give me hell if he found out — and it wasn’t my fault. Even as I had that thought, another more peevish one crept in. It was typical that Leo, with a girl in every port, should be calling forth tears of joy and sorrow, whereas no one worried at all about what happened to me. The woman in front of me had made a snorting, incredulous sound when I said Leo was dead.

“But you can’t be—” she began. Then she leaned away to the front of the van’s compartment, and picked up a thing like a flashlight from the pile of rugs.

“Give me your hand.” When I didn’t move, she reached out, raised my left hand, and pressed a switch on the side of the metal cylinder she was holding. Nothing at all happened, but she gave a groan of pure misery and slumped her head forward to her chest.

“It’s true,” she said after a few seconds. “You’re not Leo. You’re the brother, the twin brother. Not Leo at all.”

It is never flattering to feel that you are being described as an object rather than a person. To her, I was clearly the wrong thing, no substitute for Leo. I began to feel an anger that even mastered my confusion.

“Now that you seem to know who I am, maybe you’d like to return the compliment,” I said. “Who are you, and why did you ask me to follow you here? If it comes to that, how did you know I’d be here at the Zoo today?”

It was brusque, but it brought her out of her silent misery. She lifted her head and shrugged.

“I followed you here from the hospital. I thought you were Leo, and I had to talk to him. About his work.”

“So why didn’t you ask me back near the hospital?”

“It might not have been safe.” She hesitated. “Look, we must talk. I am Valnora Warren. Leo and I worked together and we were close friends.”

I leaned back on the pile of rugs and took a deep breath. If she had been close to Leo, would it be any kindness to tell her what had really happened? It would be no consolation to her to know that in a sense Leo lived on, inside me.

While I was thinking about that, another memory seemed to brush against my consciousness. I was reliving the last helicopter ride that Leo and I had made, when he told me that he needed to talk to me. There had been no time to find out why, but I could recall his worry and tension. Until I knew more about her, it seemed to me that the less I told Valnora Warren, the better.

She seemed to have herself under good control now. As our eyes became used to the dim light, I could see her peering anxiously at me, nervously rubbing her fingers along the smooth material of her dress.

“Look — Lionel, isn’t it? — I know this must seem peculiar to you. Leo and I worked together, off and on, for a long time — eight years. We were very close, so I know from what he told me that you and he were even closer.”

From the way she spoke, I sensed that she had been about as close to Leo as anyone could get. I remembered the way she had grabbed me when I first came into the van. I just nodded. “Leo and I were very close.”

“But you didn’t see each other very often, did you? I was wondering, did he ever tell you much about the work that he did?”

Her question was tentative, and I could feel a premonition building inside my head like a black thundercloud. She was too nervous. It made me aware that Leo’s own emotion, that final evening, had been more than tension. He had been afraid, eager to talk to me in a way that was quite different from the usual easy familiarity that we had built up over the years.

“We talked about his work sometimes,” I said. “We talked about everything we did.”

“You know where he had been before he came to London ?”

“He was away in the East, and on his way back to Washington .”

“Do you know where in the East?” Her intensity was painful.

“No. Look here, if you want to sit and cross-examine me you’d better start by telling me what all this is about. Otherwise, the hell with it. I’ll go back to the hospital.”

“No. Please don’t go.” She was biting her lip, trying to make up her mind about something. “I shouldn’t, but I’ll — I’ll answer some questions. Some things I just can’t talk about. But you’ll have to try and answer some of my questions, too.”

“We’ll see. I won’t make any promises.” (I couldn’t — I had no idea what information I might have that could possibly be interesting to her.)

“All right. What do you want to know?”

“For a start, what’s that thing?”

I pointed at the cylinder like a flashlight that was sitting on the rugs beside her.

“It’s an ultraviolet lamp.” She picked it up. “Leo had a small tattoo on his left wrist — invisible in ordinary light, but it would fluoresce in ultraviolet light. That’s how I knew—” She paused, and looked down.

“Is that usual for people who work for the U.S. State Department?”

She hesitated again, and leaned back against the metal panel of the van. “I can’t answer that. At least, I may be able to, but I’ll have to call and get permission. I felt so sure that you were Leo, I didn’t…” She seemed all set to disappear again in her trance of grief. “When you last saw him, did he tell you—”

“You find out if you can tell me what you know, then I’ll tell you what I know. I don’t care for all this mystery.”

“I’ll know what I can tell you by tomorrow.” She tried to force a smile. “Could we have dinner then? If you’ll do it, I promise that I’ll be able to give you answers — more than I can now.”

“Tomorrow?” The idea would make Sir Westcott choke on his apple, for me to be out two days in a row, but what the hell, he wasn’t my keeper. “Where and when?”

“In London ? Can you meet me, at, say, eight o’clock ?”

“I hope so. Whereabouts?”

“How about Bertorellis, in Charlotte Street ?”

“I know it. I’ll meet you there, if you’ll answer me one more question now.”

She looked uneasy. “If I can.”

“Was Leo’s job a dangerous one?”

She made a noise somewhere between a laugh and a sob. “You’ve been leading me on. He told you, didn’t he? I thought he might have, even though he wasn’t supposed to. Would you answer one question for me, before you go?”

“I had my turn. What do you want to know?”

“Did he ever mention to you somebody with the initials T.P.?”