“Well, I-”

“I called round the other day, which I found a most upsetting experience in view of all the happy times my late husband and I enjoyed there, but Miss Paxton wasn’t in. Of course, I suppose she uses the flat merely as a pied-à-terre. And very agreeable too. But for those of us on fixed incomes-”

“Mrs. Simpson!” I shouted.

“Yes?” she responded, briefly cowed.

“Are you saying Sarah’s taken over the lease of a flat you used to occupy?”

“I don’t understand. Surely you must know she has. Ah, Braybourne Court.” Her tone became wistful. “Such a charming corner of Chelsea.”

“Chelsea, you say?”

“Certainly.”

“Where exactly in Chelsea?”

“What an extraordinary question. Surely Miss Paxton’s told you.”

“No. As a matter of fact, she hasn’t. She, er, neglected to give me the address. Which is awkward, since I’ve promised to visit her there. So, could you enlighten me?”

She didn’t reply at once. I could almost feel her suspicion coursing down the line. “How did you say you got my number, Mr…?”

“Timariot. Robin Timariot. I’d be happy to discuss your forwarding problems with Sarah, Mrs. Simpson. More than happy. I’m sure I could sort something out on your behalf. I can also give you her Bristol address and telephone number, which you might find helpful.”

“Hmm. Miss Paxton doesn’t seem to be a very well-organized young lady, I must say.”

“Quite so.”

“Very well, Mr… er… Marriott. Braybourne Court is an apartment block in Old Brompton Road. My flat-Miss Paxton’s, that is-is number two hundred and twenty-eight. Though what kind of a friend you count her as if she can’t be bothered to supply you with such information herself I really can’t imagine.”

“No, Mrs. Simpson. Neither can I.”

The rain was unceasing, drifting in sheets across the dank green fields of Wiltshire and Berkshire as I drove towards London. I cursed the traffic and spray that slowed my progress, watched the clock tick round and the meagre light drain from the louring sky… and wondered. What would I find at 228 Braybourne Court? Why the secrecy? Why the cunning manipulation of events? What was it leading to? They’d been so clever I still couldn’t see beyond the ruse itself. But for Sir Keith’s death, of course, they’d still be safe from detection. And but for Mrs. Simpson’s obsession with some allegedly missing mail that could just as easily be caught up in the Christmas rush, there’d be no trail to follow. Only bad luck-only the unforeseeable intervention of the unpredictable-had defeated their precautions. Or had given me the chance of defeating them. For that’s all it was. An outside chance. One I had to take.

It was the last full shopping day before Christmas and London was at its clogged and crowded worst. Wearying of the crawl in from the M4 that had stretched the journey from Clifton to nearly four hours, I abandoned the car near Baron’s Court tube station and started walking through the deepening twilight. Red lights bleared at me from winding rows of cars and glimmered on Christmas trees in drawing-room windows. Danger winked out its warning as darkness gathered its strength. But I hurried on, following Louise into the forest even as night began to fall.

Braybourne Court was a large red-brick Edwardian mansion block near Brompton Cemetery, with separate security-locked entrances, each serving a dozen or so flats, spaced around its four sides. The entrance leading to flats numbered between 225 and 237 was in a quiet side-street. All I could see through the double glass doors was a plushly carpeted hallway, dividing discreetly after twenty feet or so. If I moved back to the steps spanning the basement area, I could catch a glimpse through the lofty ground-floor windows of corniced ceilings and flock-papered walls. An entry-phone system was in place to ensure this was as much of a view as unwelcome visitors ever got of the interior. Braybourne Court evidently placed a premium on privacy. And charged accordingly, I had no doubt. Sarah could easily be paying seven or eight hundred pounds a week for a pied-à-terre here. Which would have seemed absurdly extravagant-if that’s what I’d believed she wanted it for.

But it wasn’t, as the blank name-panel next to the buzzer for flat 228 somehow confirmed. Privacy wasn’t the point. Secrecy was nearer the mark. Absolute secrecy. Which I was about to penetrate.

I pressed the buzzer, got no response and pressed it again with the same result. I waited a few moments, then tried three short sharp rings. Still nothing. But somehow I wasn’t discouraged. She was there. And so was Paul. Why I didn’t know and couldn’t guess, but the intricacy of their deception convinced me of their presence. They might hope I’d give up and go away, but they’d be hoping in vain.

I pressed the buzzer again and this time kept my finger on it, counting the seconds under my breath. Before I’d reached forty, there was a click from the speaking grille and a voice I recognized with a surge of relief said: “Yes?”

“Sarah? It’s Robin. Can I come in?”

“Robin?” She sounded horrified as well as amazed.

“Yes. Can I come in?”

“What… How did you get here?”

“I’ll explain inside. It’s pretty cold and wet out here.”

“No. I… I can’t see you, Robin.”

“Don’t be ridiculous.”

“I’m not being. Please… Please go away.”

“You don’t mean that.”

“Please, Robin. Leave. It’s best, believe me. Goodbye.” There was another click as she put the phone down. I pressed the buzzer instantly, reckoning she couldn’t just walk away while it rang. Sure enough, she picked up the phone again. “There’s nothing more to be said, Robin. I want you to-”

“Paul’s with you, isn’t he? I know he is, so don’t bother to deny it. The police are looking for him.”

“What? Why?”

“Let me in and I’ll explain.”

“Do they… have this address?”

“No. But if I have to walk away from here, they will have it.”

“Don’t do this, Robin.” Her tone had altered. She seemed to be pleading with me-as much for my sake as hers. “You have no idea what you’re getting involved in.”

“Open the door, Sarah.”

“Please, I-”

“Open it.”

Several long speechless moments passed, during which a faint buzz from the grille assured me she was still on the line. Then there was a much louder buzz from the lock on the doors. And when I pushed against them they yielded.

I stepped inside. The doors swung shut behind me. Warm air and insulated silence wrapped themselves around me. I walked down the hall to the point where it divided, glanced left and saw a brass plaque on the wall inscribed 225-226; LIFT TO 229-237. Glancing right, I saw another plaque, inscribed 227-228. I headed that way, turned left, passed flat 227, rounded a bend in the corridor and saw the door to flat 228 at the far end.

It was fitted with a viewing lens, through which Sarah must have been watching out for me. The handle turned as I approached and the door slowly opened. But she didn’t move into view. All I could see inside was a stretch of carpet and a bare wall, dimly lit. I called her name, but she didn’t answer. I hesitated for a moment and called again. Still she didn’t respond. Not that it made any difference. I knew what I was bound to do. It was too late to turn back now. I reached out and touched the door. It creaked slightly on its hinges. Then I stepped forward and crossed the threshold.