‘It was soon over. I think she may have—sort of scratched—at my door. I fancy she did but I was asleep and by the time I opened my door there was nobody.’

‘I see. She intimated to me that she had something to tell you.’

‘I know. Oh, dear!’ Troy said. ‘Should I have gone to her cabin, do you think?’

‘Ah, no! No. It’s only that Miss Rickerby-Carrick has a very high opinion of you and I thought perhaps she intended—’ He hesitated and then said firmly. ‘I think I must explain that this lady spoke to me last evening. About her insomnia. She had been given some tablets—American proprietary product—by Miss Hewson and she asked me what I thought of these tablets.’

‘She offered me one.’

‘Yes? I said that they were unknown to me and suggested that she should consult her own doctor if her insomnia was persistent. In view of her snoring performance on the previous night I felt it might, at least in part, be an imaginary condition. My reason for troubling you with the incident is this. I formed the opinion that Miss Rickerby-Carrick was overwrought, that she was experiencing some sort of emotional and nervous crisis. It was very noticeable—very marked. I felt some concern. You understand that she did not consult me on the score of this condition: if she had it would be improper for me to speak to you about it. I think she may have been on the point of doing so when she suddenly broke off, said something incoherent and left me.’

‘Do you think she’s actually—well—mentally unbalanced?’

‘That is a convenient phrase without real definition. I think she is disturbed—which is another such phrase. It is because I think so that I am a little worried about this departure in the middle of the night. Unnecessarily so, I dare say.’

‘You heard the telephone message, just now?’

‘Yes. A friend’s illness.’

‘Can it,’ Troy exclaimed, ‘be Mavis?’

She and Dr Natouche stared speculatively at each other. She saw the wraith of a smile on his mouth.

‘No. Wait a bit,’ Troy went on. ‘She walked up to the village with Mr Lazenby and me. My head was swinging with migraine and I scarcely listened. He might remember. Of course she talked incessantly about Mavis. I think she said Mavis is in the Highlands. I’m sure she did. Do you suppose Miss Rickerby-Carrick has shot off by taxi to the Highlands in the dead of night?’

‘Perhaps only to Longminster and thence by train?’

‘Who can tell! Did nobody hear anything?’ Troy wondered. ‘I mean, somebody must have come on board with this news and roused her up. It would be a disturbance.’

‘Here? At the stern? It’s far removed from our cabins.’

‘Yes,’ Troy said, ‘but how would they know she was back here?’