‘I suppose that is so. Then our next point is: What might have been Boirac’s motive?’
‘That’s not hard to find. If Boirac found his wife was carrying on with Felix, it might explain his desire to kill her.’
‘Yes, and it would give a two-fold reason for his working for Felix’s conviction; first, self-defence by shifting over the suspicion, and, second, revenge on the man who had spoilt his home.’
‘Quite. I think a plausible motive might be built up. Next let us ask, When was the body put in the cask?’
‘The police say in London, because there was no opportunity elsewhere.’
‘Yes, and to me it seems a quite sound deduction. Now, if that is true, it follows that if Boirac killed his wife, he must have travelled here to do it.’
‘But the alibi?’
‘Leave the alibi for a moment. Our defence must be that Boirac followed his wife to London and murdered her there. Now can we suggest possible details? He would arrive at his house on that Sunday morning and find his wife gone, and a letter from her saying she had eloped with Felix. What, then, would he do?’
Clifford leaned forward to stir the fire.
‘I have thought over that,’ he said somewhat hesitatingly, ‘and I have worked out a possible theory. It is, of course, pure guesswork, but it fits a number of the facts.’