At the best, you will be given up to the police.

At the worst, I shall deal with you myself.
With the police you may have a chance--you may get off with twenty years' penal servitude, because, though it is absolutely certain that you murdered Reginald Dimmock, it would be a little difficult to prove the case against you.

But with me you would have no chance whatever.

I have a few questions to put to you, and it will depend on how you answer them whether I give you up to the police or take the law into my own hands.

And let me tell you that the latter course would be much simpler for me.