‘I’d like to oblige both you and Miss Drew,’ he said, ‘but I’m not just sure that I ought. However, as you say, it’s not exactly on the case, and if you give me your word to keep the thing to yourself I’ll tell you.’ ‘I promise most gratefully.’ ‘Very well. The man has an alibi,’ and Tanner repeated Cosgrove’s story of the visit to Montrose, the missing of the 7.15, the return to his rooms, the call at the theatre on Miss Belcher, and the final journey north by the 10.30. Then he explained how he had checked Cosgrove’s statements, and produced his calculation of times and distances, showing that Cosgrove could not have motored to Luce Manor. To Daunt the whole thing seemed utterly conclusive. Apart from the mere fact that it had satisfied Tanner—no mean test—he could not himself see any possibility of a flaw. With considerable apprehension of the disappointment Lois would feel, he telephoned to her and arranged their consultation for that evening. She heard his story almost in silence. But she did not show the chagrin he expected. ‘If the thing was obvious,’ she said in answer to his comment, ‘Cosgrove would have been arrested and not Austin. But I feel absolutely certain that that alibi of Cosgrove’s is a fraud. He has tricked Inspector Tanner. How he has done it is what you’ve got to find out.’ ‘My dear girl,’ Daunt remonstrated, ‘it’s all very well to talk like that, and I’ll do my best of course, but you know, if Tanner with all his opportunities was taken in, it’s not too likely I shall find the flaw.’ ‘It’s quite likely,’ she declared. ‘Inspector Tanner was not specially looking for a flaw; you are. Don’t you see—there must be a flaw. Look at it like this. A man resembling Austin was met by Sir William at the boathouse on that Wednesday night. It _must_ have been Cosgrove, because no one else is sufficiently like Austin to be mistaken for him. No kind of facial make-up will meet the case, because Sir William himself evidently was satisfied. Therefore Cosgrove’s alibi must be false. Don’t you agree with me?’ ‘It seems reasonable,’ Jimmy admitted. ‘But the alibi certainly looks right enough too.’ ‘I admit that. It may be so good that we’ll never find the flaw. But we must try. Oh, Jimmy,’ she turned to him beseechingly, ‘remember what is at stake—his life—both our lives. You will try, won’t you?’ ‘Of course I’ll try, and what’s more, I expect to succeed,’ Jimmy lied bravely. And he spoke in the same confident tone as, after dinner, he went to the station with her, and saw her off by the 9.30 to Halford. But his secret feelings were very different. Two days later he had another call from Lois. ‘You needn’t be frightened,’ she smiled at him; ‘I am not going to haunt the office and make your life a burden to you. But I have been thinking over our problem. I want you, Jimmy, to begin an investigation. Will you?’ ‘Why certainly, if I can. What is it?’