‘If we must find the real murderer we may as well let the case alone. If Scotland Yard and the Sûreté couldn’t get him, we are not likely to.’
‘You haven’t quite got me. I don’t say we must find him. It will be enough to suggest him. All we have to do is to show that some other person had a motive for Madame’s death, and could have murdered her and carried out the plot against Felix. A doubt would then arise as to which of the two was guilty, and, if that doubt was strong enough, Felix would get the benefit of it.’
‘But that makes our problem no easier. The difficulty still lies in the finding of this other person.’
‘We can only try; it may lead to something. Our first question then is: If Felix is innocent, who might be guilty?’
There was silence for several seconds, then Heppenstall spoke again.
‘Who, perhaps I should say, is least unlikely to be guilty?’
‘I think there can be only one answer to that,’ returned Clifford. ‘In the very nature of the case a certain suspicion must attach to Boirac. But the police were fully alive to that. From all we hear, they went into it thoroughly and came to the conclusion he was innocent.’
‘It depended on an alibi. But you know as well as I do alibis can be faked.’
‘Undoubtedly, but they concluded this one wasn’t. We don’t know the exact details, but it seems to have been fully tested.’
‘At all events, from the information available, I think we may assume that if Felix is innocent, Boirac is guilty. There is no suggestion of any third party being involved. If, then, we can show that Boirac had a motive for the crime, and that he could have committed it and made the plant, that’s all we want. We have not to prove him guilty.’