“I subconsciously registered that there was something different about the roof, but I didn’t really focus on what it was because it was too far from the room where Lorna died to have anything to do with the murder, I thought at the time. Last night, however, I stood at the same window and I remembered what I’d seen. It hadn’t been there on Saturday afternoon, and it wasn’t there when I looked out again on Tuesday. But it was on Saturday night.”

The percolator burped loudly as Lindsay paused for dramatic effect. She grinned and went on. “Four scaffolding poles and a pile of clamps. And I thought, what if someone put them together and clamped them to the railings? They could clamber along the frame, wait till Lorna was making enough noise to cover small sounds, slide up the window catch almost silently, as I did the other day with my knife, get into the room, creep up on her, and kill her. All the setting up could have been done while everyone else was having dinner. The garrote could have been made at any time during that afternoon, or even at dinner time. I also had a wander round the building site for the squash courts. There’s lots of scaffolding poles there that look just the same as the bits on the roof.”

There was a pause as Cordelia considered these new possibilities. “I think we both need that coffee now,” she said softly. She left the room and returned with two steaming mugs.

“That certainly answers one or two questions,” she sighed.

“All of them except the crucial one,” Lindsay replied. “It explains why no one saw the murderer entering or leaving the room. It also explains the problem of the locked door. All the murderer had to do beforehand was to arrange the chair and music stand so that Lorna had her back to the window, to check out the window catches, and to collect a cello string—a gruesome little touch. And if I’m right, it also cuts the suspects down considerably.”

“I suppose so,” said Cordelia meditatively. “I haven’t had long enough to assimilate the idea yet. Surely, though, it lets out Paddy and Margaret for a start?”

“I reckon it eliminates everyone who was visible or alibied at dinner and during the first half of the concert. That does mean Paddy and Margaret—and also Caroline and Jessica. And of course, you. There’s no way you could have been shinning up scaffolding in that outfit! And much to my irritation I think we may have to exclude James Cartwright. It’s got to be someone who had motive, means, and opportunity, but also the skill and nerve to contemplate that particular murder method. Right now I can think of only one person who fits the bill.”

“The one man we haven’t seen yet.”