Norman West was out. I phoned him on the hour at four and five and reached him at six. He said apologetically that he had stopped working on the Pembroke case, there was nothing else he could do. He was sorry he hadn't been able to solve the… er… problem, and should he send his account to Mr Pembroke at the Savoy, or at Quantum House?

"Neither," I said. "We'd like you to carry on working." And I told him what had happened to Quantum and very nearly to ourselves.

"Dear me," he said.

I laughed internally, but I supposed "dear me" was as apt a comment as any.

"So would you mind traipsing all the way round again to ask what everyone was doing the day before yesterday between three p.m. and midnight?"

He was silent for an appreciable interval. Then he said, "I don't know that it would be useful, you know. Your family were unhelpful before. They would be doubly unhelpful again. Surely this time the police will make exhaustive enquiries? I think I must leave it to them."

I was more dismayed than I expected. "Please do reconsider," I said. "If the police go asking the family their movements, and then you do also, I agree they won't like it. But if after that I too go and ask, they may be upset enough or angry enough to let out things that could tell us… one way or another." I paused. "I suppose I'm not making much sense."

"Do you remember what you said to me about stepping on a rattlesnake?" he said.

"Well, yes."

"You're proposing to stir up one with a stick."

"We absolutely have to know who the rattlesnake is."

I heard him sigh and could feel his disinclination.

"Look," I said, "could you just meet me somewhere? You gave my father and me summaries of what all the family were doing on those two days we asked about, but there must be much more you could tell me. If you don't want to visit them again, could you just… help me."

"I don't mind doing that," he said. "When?"

"Tonight? Tomorrow?"

Tonight he was already working. Tomorrow he was taking his wife to visit their grandchildren all day as it was Sunday, but his evening would be free. He knew the pub I was staying in, he would come there, he said; he would meet me in the bar at seven.

I thanked him for that anyway, and next telephoned two stables along on the Downs to ask the trainers if I could ride exercise on their horses for several mornings, if it would be useful to them. The first said no, the second said yes, he was a couple of lads short and he'd be glad of the free help. Start Monday, first lot, pull out at seven-thirty, could I be there by seven-fifteen?

"Yes," I said appreciatively.

"Stay to breakfast."

Sanity lay in racing stables, I thought, thanking him. Their brand of insanity was my sort of health. I couldn't stay away for long. I felt unfit, not riding.

I spent the evening in the bar in the pub, mostly listening to a lonely man who felt guilty because his wife was in hospital having her guts rearranged. I never did discover the reason for the guilt, but while he grew slowly drunk, I learned a lot about their financial troubles and about his anxieties over her illness. Not a riotously amusing evening for me, though he said he felt better himself from being able to tell a perfect stranger all the things he'd been bottling up. Was there anyone at all, I wondered, going to bed, who went through life feeling happy?

I dawdled Sunday away pleasurably enough, and Norman West, true to his word, appeared at seven.

His age was again very apparent from the grey-white hair downwards, and when I remarked that he looked tired, he said he'd been up most of the previous night but not to worry, he was used to it. Had he been to see his grandchildren? Yes, he had: lively bunch. He accepted a double scotch with water and, under its reviving influence, opened the large envelope he was carrying and pulled out some papers.

"Your photographs of the family are in here," he said, patting the envelope, "and I've also brought these copies of all my notes." He laid the notes on the small table between us. "You can have them to keep. The originals are in my files. Funny thing," he smiled, "i used to think that one day I'd write a book about all my cases, but there they are, all those years of work, sitting in their files, and there they'll stay."

"Why don't you write it?" I asked.

"I'm better at following people."

I reflected that following people was what he'd been good at when Joyce had first employed him, and that probably we'd expected too much of him, setting him to unravel attempted murders.

He said, "You'll find there's a definite pattern about the movements of your family, and at the same time an absence of pattern. The murder of Mrs Moira and the gassing of Mr Pembroke both took place at about five in the evening, and at five almost all your family are habitually on the move. Mind you, so is most of the working population. It's a time of day when it's easy to lose an hour or so without anyone noticing. Traffic jams, left work late, stopped for a drink, watched television in shop windows… I've heard all those from erring husbands. The list is limitless of things people think up as excuses for getting home late. With a family like yours, where practically no one has a set time for leaving a place of work, it's even easier. That's why it's been almost hopeless establishing alibis, and I'm pretty sure the police found the same thing over Mrs Moira. When there's no expectation of anyone arriving at a regular time, no one looks at the clock."

"I do understand," I said thoughtfully.

"Newmarket was a bit different," he said, "because it meant someone being away from their normal environment for a whole day, assuming that Mr Pembroke was followed from his hotel when he left at lunchtime for Newmarket. And one has to assume that a follower would be in position much earlier than that, because he wouldn't know when Mr Pembroke would leave, or where he would go." He cleared his throat and sipped his whisky. "I thought it would be simple in those circumstances to discover which family member had been away all of that Tuesday, but in fact it wasn't, as you'll read. Now, if the explosive device was planted in Quantum House between four when the gardener usually left and six, when you might have returned from the races, we're back to the… er…"

"Five o'clock shadow," I said.

He looked mildly shocked. It wasn't a laughing matter. "I've no doubt the same pattern will be found," he said. "No one will be able, or willing, to say exactly where they were or where anyone else was during that period."

"We may be lucky," I said.

He said maybe, and looked unconvinced.

"Couldn't you please tell me," I said, "which Mrs Pembroke got you to find Malcolm? I know all about your ethics, but after this bomb… can't you? Whose name was on the cheque?"

He considered, staring at his drink as if to find wisdom in the depths. He sighed heavily, and shrugged.

"I didn't get paid," he said. "The cheque never came. I'm not sure, but I think… I think it was the voice of Mrs Alicia Pembroke." He shook his head. "I asked her if it was her, when I interviewed her. She said it wasn't but I think she was lying. But two other people found out on their own account, don't forget, by doing exactly as I did, telephoning around."

"I won't forget."

He looked at me sombrely. "I hope Mr Pembroke can't be found as easily at this moment."

"I don't think so," I said.

"Can I give you some advice?"

"Please do."

"Carry a weapon with you."

"Mr West!"

"Even if it's only a pot of pepper," he said, "or a can of spray paint. There's a good deal of enmity towards you in your family because of your favoured status with Mr Pembroke. You were supposed to die with him in the house, I should imagine. So don't go unprepared."