Unknown is built around a tantalizing premise: a man (Jim Caviezel) wakes up in a deserted warehouse surrounded by several other seemingly dead men. He has absolutely no memory of who he is or how he got there, and he is unable to get out. Before too long, the others (including Joe Pantoliano and Greg Kinnear) wake up and they all have amnesia, too.

All they know is that some of them have been shot, one is tied to a chair, the dead body of a security guard has been stuffed into a locker, and soon they figure out that two of them have been kidnapped by the other three. Who are the kidnappers and who are their victims?

This sounds a little like the famous "Monsters are Due on Maple Street" episode of The Twilight Zone episode, with some elements seemingly taken from the Law School Admissions Test. ("There are five men in a warehouse. Two have been kidnapped by the other three. If A is a kidnapper, B must be a victim. C and D were working together...")

It's an interesting idea. For the first hour, director Simon Brand does a good job keeping the viewer guessing while the characters team up with and turn against each other. Unfortunately, Unknown is 85 minutes long and it falls apart in its final third.

Roger Ebert's Little Movie Glossary describes the "Law of Economy of Characters" as follows: "All characters in a movie are necessary to the story - even those who do not seem to be. Sophisticated viewers can use this law to deduce the identity of a person being kept secret by the movie's plot: This 'mystery' person is always the only character in the movie who seems otherwise extraneous." Unknown includes a perfect example, with one character (whose identity I will not reveal) appearing completely redundant unless that character's role is very different from what we're led to believe.

The DVD packaging for Unknown describes the film as being "in the vein of The Usual Suspects and Memento," so you will not be surprised to find out there's a surprise twist ending -sort of. I watched it twice and instead of making me see the film in a whole new light, I found myself thinking, "That's it?"

Unknown is good enough to hold your interest for 85 minutes, but that's about it. I may not have amnesia, but I did find it pretty forgettable.