This could actually be the Martian Manhunter episode, I know nothing about Martian Manhunter but some people are saying it could be him.
From the TWoP Forums:
Garett Graham, the FOTW, mentions a couple of times that he is a "head hunter" - that he tracks people down for large sums of money. That's why Clark gets the idea that he's a bad guy. Add to the "head hunter" mentions 1) the interest in Nois, 2) he's untraceable, and 3) possibly hinting he can read minds, and I'd say they decided to give Martian Manhunter his own episode instead of making him the sheriff. And they gave him invisibility as a power - which I guess fits with the ability to control your appearance.
Garett is a head hunter and he gets paid a lot of money to find people, but it's unclear who he is tracking in the episode. The two situations may be connected.
In the comics, Martian Manhunter has been both a Detective in the police force, and later a private detective, so that would loosely tie into the head hunter thing. There was also made mention that he kept an eye on Clark as a baby in Smallville, so it would actually fit for him to be on the show, believe it or not. Usually, he goes by the identity of John Jones, but he's been known to take others.