At the present stage of the inquiry there are, as I take it, three discoveries to make, starting from that smear.

Find out (first) whether there is any article of dress in this house with the smear of the paint on it.

Find out (second) who that dress belongs to.
Find out (third) how the person can account for having been in this room, and smeared the paint, between midnight and three in the morning.
If the person can't satisfy you, you haven't far to look for the hand that has got the Diamond.

I'll work this by myself, if you please, and detain you no longer-from your regular business in the town.

You have got one of your men here, I see.