It was a very uncomfortable minute for me. I hardly took in what happened next, but when I was sufficiently in control of myself to realize what was going on, Ralph Paton was standing by his wife, smiling across the room at me. Poirot, too, was smiling, and at the same time shaking a finger at me. 'Have I not told you many times that it is useless to conceal things from Hercule Poirot?' he demanded. 'That he always finds these things out?'

He turned to the others. 'One day, you remember, I accused five persons of concealing something from me. Four of them told me their secret. Dr Sheppard did not.'

'I suppose I might as well explain things now,' I said. 'I had been to see Ralph that afternoon. He told me about his marriage, and the trouble he was in. As soon as the murder was discovered, I realized that suspicion would fall on Ralph - or on the girl he loved. That night I told him the facts. The thought of having to give evidence which might incriminate his wife made him decide at all costs to - to-'

I hesitated, and Ralph spoke up. 'To disappear,' he said.

Ursula took her hand from his, and stepped back. 'You thought that, Ralph! You actually thought that I might have killed your stepfather?'

'Let us return to the behaviour of Dr Sheppard,' said Poirot drily. 'Dr Sheppard was successful in hiding Captain Paton from the police.'

'Where?' asked Raymond.

'You should ask yourself the question that I did. If the doctor is concealing the young man, what place would he choose? It must be nearby. I think of a hotel? No. Where, then? Ah! I have it. A nursing home. A home for the mentally ill. So in order to investigate further, I invent a nephew with mental trouble. I ask Mademoiselle Sheppard about suitable homes. She gives me the names of two near Cranchester to which her brother has sent patients. I make inquiries. Yes, at one of them a patient was brought by the doctor early on Saturday morning. Though known by another name, I had no difficulty in identifying that patient as Captain Paton. After certain formalities. I was allowed to bring him with me to my house in the early hours of yesterday morning.'

'Dr Sheppard has been very loyal,' said Ralph. 'He did what he thought was best. I know now that I should have come forward, but in the nursing home, we never saw a newspaper or heard the radio. I knew nothing of what was going on.'

'Well, now we can have your story of what happened that night,' said Raymond impatiently.