The man does look vaguely familiar to the Dodger, and he finds himself staring a little. He's not picking him out as a mark - not so much as he reckons - but he's trying to place where he knows him from.

So he follows the bloke, of course he does. Trying to work out where he knows him from, and if it's a good knowing or not. It could just be that he's got one of those faces.