“It’s my own fault. I should have asked you this when I spoke to you before. But I let myself be sidetracked when you told us where you found Miss Callaghan and what frame of mind she seemed to be in. Daft of me—because I asked everyone else what I’m going to ask you now. I had a feeling it might be important. All I wondered was if you saw Sarah at all on Saturday night, and if so, when and where.”

“Is that all?” she said, sounding relieved. “I actually saw her a couple of times. When I went to get my coat to go across to Main Building to get Miss Callaghan, Sarah was just going out of Longnor. She had her anorak on and she was wearing tracksuit bottoms and trainers.”

“What time was that?”

“It must have been about a quarter past seven. I remember looking at my watch and thinking that was good because I’d be able to find Miss Callaghan before the concert started. Then, when we came back, I went back into the cloakroom to hang my coat up. That must have been just after half-past seven—say, twenty-five to eight. Sarah was sitting in the cloakroom, just staring into space, I tried to talk to her, but she just shrugged me off and I saw her going back upstairs. I suppose she was going back to her room. It’s terrible to think of it now—she must have just come back from killing Lorna then, mustn’t she?”

Lindsay was noncommittal, trying not to show that what the girl had said was significant. She thanked Jessica for her help and as gently as possible got rid of her. She sat at Paddy’s desk with her head in her hands. What she had just been told made her thoughts race furiously round her head. How could Sarah have killed Lorna between seven fifteen and seven thirty-five? Although that part of the school grounds overlooked by the music-room windows was normally dark and deserted at that time of the evening, on the night of the murder it had been busy: cars were being parked and people were walking to the concert. It would not have been feasible to have carried out that murderous climb until the area had been quiet again—in other words, till seven thirty. And Lindsay couldn’t believe the murderer would have taken any chances till the concert was under way, to muffle any sounds coming from the music room.