I don't know what movie the other posters here saw, but if it was the same one as me, they really need to get out more. This movie is an eyesore. Where can I begin? To be fair, I think the basic story is good. Or could be, with a little work. However, the script is choppy as hell with absolutely no flow to it. We're supposed to believe that just because a bad script confuses us with one unrelated scene to another filled with droning dialog, it's an intriguing mystery. Confusion does not equal mystery. We're confused not because of the mystery story, but because there's not any solid story there!
In fact, the script wanders so much we're confused about what the film's really about: an art theft? No. One man's struggle to steady his failing career & relationships? No. Some sort of confidence game? Maybe. The author tries hard to make this appear like a real mystery / suspense film using cliché and mysterious, hush-hush, unrevealing dialog.
A good mystery will lead you down one or two false paths and surprise you at the end. A good suspense film will have you wondering what's around the next corner; what's going to happen next? This movie bores you to death leading you nowhere, then has a puerile ending a 10-year-old could see from a mile off. The only surprise is that you actually sat through it all. If you did.
One person compared this to Mamet's Spanish Prisoner. Not even close. The only similarity is that both look like plays. That is, lots of dialog. Collusion is full of long scenes with endless chatter about nothing. That, and long scenes forcing us to watch boring night club singers. My script coach would chop this thing down to about 15 minutes of screen time. Maybe it should have been a short film? I hope the actors got paid well. I've seen them in other films and it's hard for me to blame them for this film's outcome. 3 out of 10.