Agatha Christie: Peril at End House

'I will look after her,' said Lazarus. 'My business is in a bad way, but I believe I shall pull through. And if I don't-well, Frederica does not mind being poor-with me.'

She shook her head, smiling.

'It is late,' said Poirot, looking at the clock.

We all rose.

'We have spent a strange night in this strange house,' Poirot went on. 'It is, I think, as Ellen says, an evil house…'

He looked up at the picture of old Sir Nicholas. Then, with a sudden gesture, he drew Lazarus aside.

'I ask your pardon, but, of all my questions, there is one still unanswered. Tell me, why did you offer fifty pounds for that picture? It would give me much pleasure to know-so as, you comprehend, to leave nothing unanswered.'

Lazarus looked at him with an impassive face for a minute or two. Then he smiled.

'You see, M. Poirot,' he said. 'I am a dealer.’

‘Exactly.'

'That picture is not worth a penny more than twenty pounds. I knew that if I offered Nick fifty, she would immediately suspect it was worth more and would get it valued elsewhere. Then she would find that I had offered her far more than it was worth. The next time I offered to buy a picture she would not have got it valued.'

'Yes, and then?'

'The picture on the far wall is worth at least five thousand pounds,' said Lazarus drily.

'Ah!' Poirot drew a long breath.

'Now I know everything,' he said happily.