“Robin may stay and listen too, mayn’t she?” asked Henry.

“Certainly. In a sense,” said Alleyn, “Miss Grey is the heroine in this case.”

“I am?” asked Roberta. “How can that be?”

“Your statement last night gave us the first inkling as to Giggle’s activities. You remember that you told us how, when you were alone in the dining-room, you heard the lift. Do you mind repeating that story once more?”

“Of course not. I heard Lord Wutherwood call out the second time. Then I heard the lift go down. Then I took a cigarette. Then I heard the lift again. Coming up. Then I hunted for matches and leant out of the window, smoking and listening to London. Then I heard Lady Wutherwood scream. The screams got louder and louder as…” Roberta stopped and stared at Alleyn. “Now I see,” she said slowly. “That’s why you made me repeat it twice over. The lift noises didn’t fit with the screams.”

“That’s it,” said Alleyn. “You see, according to all the other evidence, Lady Wutherwood began screaming while the lift was still going down and all the time it was coming up. But you heard the lift go down and come up with no disturbance. Then you leant out of the window and listened to London so you didn’t hear the lift go down on the second trip. You only heard her scream as it returned.”

“So there was a trip down and up unaccounted for,” said Henry.

“Yes. But the commissionaire said positively that the lift only made one trip and that the fatal one, when your brother stopped it before it actually reached the ground floor but when it was within view of the hall. What of this other trip? The only explanation was that it didn’t go all the way down. Now, when Miss Grey heard the lift, Michael and Giggle had just left her. They both say that Giggle went straight downstairs. Yet Giggle stated that the lift made no movement while he was going downstairs. He swore that it was at the top landing with Lord Wutherwood inside. It is at least true that Lord Wutherwood was inside. But we know it went down and we know Giggle must have seen it. The lift can be summoned from any floor at any time. The flat on that landing below yours is unoccupied. Our theory is that Giggle, on leaving Michael, went down to that landing. Michael saw him go and went into Flat 26. That gave Giggle his dubious alibi. He summoned the lift with Lord Wutherwood inside it. He entered the lift and inflicted the injuries. He was wearing your motoring gloves. He threw them under the seat, got out of the lift and went on down to the ground level where the commissionaire spoke to him. He then walked through the front entrance and got into the car.”

“But why!” Henry said. “Why did he kill him?”