You go to Hardyman's bankers, with a note in Hardyman's handwriting (exactly imitated by me) to this effect:--'Mr.H.presents his compliments to Messrs.

So-and-So, and is not quite certain whether a payment of five hundred pounds has been made within the last week to his account.

He will be much obliged if Messrs.

So-and-So will inform him by a line in reply, whether there is such an entry to his credit in their books, and by whom the payment has been made.' You wait for the bankers' answer, and bring it to me.
It's just possible that the name you're afraid to whisper may appear in the letter.

If it does, we've caught our man.