"What are you doing?" he screamed.

"Preparations," I said. "I always have to make the right preparations before I kill someone."

"Help," he yelled. But I had left the television on with the volume turned up, and his shout was drowned out by some advertisement music.

However, to be sure that he wouldn't be heard, I took a piece of the duct tape and fixed it firmly over his mouth to stop him from yelling again. Instead, he began breathing heavily through his nose, hyperventilating, his nostrils alternatively flaring and contracting below a pair of big frightened eyes.

"Now then, Alex," I said, in as calm a manner as I could manage. "You seem not to fully appreciate the rather dangerous predicament in which you have found yourself." He stared at me unblinkingly. "So let me explain it to you. You have been blackmailing my mother to the tune of two thousand pounds per week for the past seven months, to say nothing about the demands on her to fix races. Some weeks you collect the money yourself from the mailbox in Cheap Street, and sometimes you get Julie Yorke to collect it for you."

I removed the three prints of the photos I had taken of Julie through the window of the Taj Mahal Indian restaurant and held them up to him. With the tape on his mouth, it was difficult to fully gauge his reaction, but he went pale and looked from the photos to my face with doleful, pleading eyes.

"And," I went on, "you are blackmailing my mother over the knowledge you have that she has not been paying the tax that she should have been. Which means you either have her tax papers in your possession or have had access to them."

I reached down into my rucksack and again brought out the red "anti-AIDS" kit. If anything, Alex went paler.

"Now, my problem is this," I said. "If I let you go, you will still have my mother's tax papers. And even if you give me back the papers, you would still have the knowledge."

I took the large syringe out of the kit, attached a new needle, and then drew up a large quantity of the saline solution from the bag that was still hanging on the stair banister, the bag with the insulin label.

"So you see," I said, "if you won't help me, then I will have no alternative but to prevent you from speaking to the tax authorities."

I held the syringe up to the light and squirted a little of the fluid out in a fine jet.

"Did you know that insulin is essential for proper body functions?" I asked. "But that too much of it causes the glucose level in the blood to drop far too low, which in turn triggers a condition called hypoglycemia? That usually results in a seizure, followed by coma and death. Do you remember the case of that nurse, Beverley Allitt, who killed those children in Grantham hospital? Dubbed the Angel of Death by the media, she murdered some of them by injecting large overdoses of insulin."

I knew because I'd looked that up on the Internet as well.

I touched his foot.

"And do you know, Alex, if you inject insulin between someone's toes it is very difficult, if not impossible, to find the puncture mark on the skin, and the insulin would be undetectable, because you create it naturally in your body? It would appear you died of a seizure followed by a heart attack."

The statement wasn't entirely accurate. The insulin used nowadays to treat diabetics is almost exclusively synthetic insulin, and it can be detected as being different from the natural human product.

But Alex wasn't to know that.

"Now, then," I said, smiling and holding up the syringe to him again. "Between which two toes would you like it?"

I was worried that he was going to pass out. His eyes started to roll back in their sockets, and his breathing suddenly became shallower. I didn't want him to have a heart attack simply from fear. That might take some explaining.

"Alex," I shouted at him, bringing his eyes back into focus on my face. "You can prevent this, you know. All you have to do is cooperate and answer all my questions. But you have to be completely candid and tell me everything. Do you understand?"

He nodded eagerly.

"And do you agree to answer everything?"

He nodded again.

"Nothing held back?"

He shook his head from side to side, so I stepped forwards and tore off the tape from across his mouth.

"Now, for a start," I said, "who killed Roderick Ward?"

He still wouldn't answer.

"I won't give you another chance," I said seriously.

"How do I know you won't kill me anyway, after I've told you?"

"You don't," I said. "But do you have any choice? And if I gather enough incriminating information about you, so that you would also be in big trouble if you told the tax man about my mother, then we would both have a weapon of mass destruction, as it were. Either of us telling the authorities would result in the very thing we were trying so hard to prevent. We would both have the safety of mutually assured annihilation, a bit like nuclear deterrence. Neither of us would use the information for fear of the retaliation."

"But you could still kill me," he said.

"Yes," I agreed, "I suppose I could, but why would I? There would be no need, and even I don't kill people without a reason."

He didn't look terribly reassured, so I untaped his foot from the spindle and then pulled him across the floor so he was sitting up with his back against the wall by the kitchen door.

"Now," I said, sitting down once more on the upright chair. "If you didn't kill Roderick Ward, who did?"

I still wasn't sure he would tell me, so seemingly absentmindedly, I picked up the syringe and made another fine spray of fluid shoot from the needle.

"His sister," Alex said.

I looked at him. "Stella Beecher?"

He seemed surprised I knew her name, but I'd already shown him the note he had sent to her. He nodded.

"Now, why would she kill her own brother?"

"She didn't mean to," he said. "It was an accident."

"You mean the car crash?"

"No," he said. "He was already dead when he went into the river. He drowned in a bath."

"What on earth was Stella Beecher doing giving him a bath?"

"She wasn't exactly giving him a bath. They were trying to get him to tell them where the money had gone."

"What money?" I asked.

"Fred's father's money."

I was confused. "Fred?"

"Fred Sutton," he said.

Old Man Sutton's son. The man I had seen in the public gallery at Roderick Ward's inquest.

"So Fred Sutton and Stella Beecher know each other?" I asked.

"Know each other!" He laughed. "They live together. They're almost married."

In Andover, I thought, close to Old Man Sutton and his nursing home. So it had been no coincidence at all that Stella Beecher had moved to Andover.

It took more than an hour, but in the end, Alex told me how, and why, Roderick Ward was found dead in his car, submerged in the River Windrush.

Ward had been introduced to Old Man Sutton by Stella Beecher, who had been in a relationship with Detective Sergeant Fred for some time. Unbeknownst to either Fred or Stella, Roderick had somehow conned the old man into borrowing against his house and investing the cash in a nonexistent hedge fund in Gibraltar. Fred found out about it only after he'd seen the brick being thrown through his father's window. It was like a soap opera.

"How do you know all this?" I asked Alex. "What's your connection?"

"I worked with Roderick Ward."

"So you are implicated in this sham hedge-fund business?"

He didn't really want to admit it. He must have known that my mother had been conned in the same way. He looked away from my face, but he nodded.

"So who's the brains behind it?" I asked.

He turned his eyes back to mine. "Do you think I'm stupid or something?" he said. "If I told you who it was then you wouldn't need to kill me because they'd do it for you."