Kate said, “Didn’t she admit as much when Kimberley and Dean brought up the tea?”

Benton said, “She certainly seemed to prefer Kimberley Bostock to Sister Holland. Seems reasonable to me, sir. Mrs. Bostock wondered whether she should have the tea, as she was having an operation the next morning. She knew she ought to check with Sister Holland. Leaving Dean standing outside Mrs. Skeffington’s suite, she knocked on Sister’s door and peered in.”

Kate said, “She said she heard quarrelling. Chandler-Powell said talking. Whichever it was, Chandler-Powell obviously feels his admission provides an alibi for both him and Sister Holland. Of course, that depends on the actual time of death. He claims to be unsure exactly when he went to Sister Holland’s suite, and she, too, is surprisingly vague. By leaving the time so uncertain, they avoided the mistake of claiming an alibi for the actual time of death, which is always suspicious, or leaving themselves with no alibi. It’s possible that by the time they were together, one or both of them had killed Rhoda Gradwyn.”

Benton said, “Can’t we be a little more precise about the time of death? Mrs. Skeffington says she heard the lift descending when she first woke up and before she rang for tea. She put that at about eleven-forty. The lift is opposite Sister Holland’s suite, at the end of the corridor, and it’s modern and comparatively quiet. But we’ve checked, and it’s perfectly possible to hear it if there’s no other noise.”

Kate said, “But there was. Apparently the wind gusted quite strongly last night. But if she heard it, why didn’t Sister Holland? Unless, of course, she and Chandler-Powell were in the bedroom and too busy quarrelling to hear. Or having sex, which doesn’t exclude quarrelling. Either way, there’s no hope of expecting Kimberley to stand firm on her evidence.”

Benton went on without commenting. “If they’d been in the sitting room, one of them would surely have heard Kimberley when she knocked on the door or seen her when she half opened it. No one admits to using the lift that night at any time except the Bostocks when they brought up the tea. If Mrs. Skeffington’s evidence is accurate, it seems reasonable to place the time of death at about eleven-thirty.”

Glancing at Dalgliesh, Benton paused and Kate took over. “It’s a pity she can’t be more accurate about the time when she heard the lift and saw the lights. If there’s a significant difference between them—longer, for example, than it would take to walk from the bottom of the lift to the stones—then there must be two people involved. The murderer can’t be descending in the lift and shining a torch at the stones at the same time. Two people, maybe two different enterprises. And if there was collusion, the two obvious suspects are the Westhalls. The other significant evidence is Dean Bostock’s statement about the unbolted back door leading to the lime walk. The door has two security locks, but Chandler-Powell is adamant he bolts it every night at eleven o’clock unless he knows a member of the household is still out. He’s absolutely sure he bolted the door as usual, and found it bolted in the morning. The first things he did after getting up at six-thirty were to turn off the alarm system and check the west door to the lime walk.”