Dark City offers one of the most compelling explanations as to what happens when people are abducted by aliens.
The story begins when John Murdoch (Rufus Sewell) awakens without any memory of his past, and is immediately forced to run from the police who want him in connection with the murder of six prostitutes. However, the police aren't the only ones who want him. A group of pale-faced long-overcoat wearing "Strangers" are also searching for him. The Strangers turn out to be a race of aliens possessing a collective consciousness (à la the Borg from Star Trek) who perform experiments on the humans they have captured in an attempt to understand, and eventually emulate, the human psyche. To this end, they plant memories into their captives and see how the humans respond to lives that they believe have lived all their lives, but are completely fictitious.
Thanks to the resilience of the human species, Murdoch manages to evolve the ability to "tune", the same ability that enables the Strangers to change the environment to suit each new experiment. This makes him the only hope of salvation for the human prisoners and, consequently, the biggest threat to the Strangers, since like them, he too can make every thought become reality.
The main reason to see this movie is for the stunning visuals, which complement the plot perfectly. The film is done in classic comic book style. It wouldn't have surprised me if words illustrating explosions and fights started appearing on the screen. Unlike many people, I wasn't too impressed by the visuals in The Crow or even The Fifth Element, to cite a couple of recent examples. But Dark City is a movie where the visuals went beyond my expectations. The morphing buildings themselves tell the tortured story of a collection of humans whose very identities are mutated and changed by the Strangers the same way the buildings are.
The plot is nothing original---it culls ideas from Star Trek (in fact, a recent episode of Star Trek: Voyager titled The Killing Game had a similar theme), The Twilight Zone, and The Outer Limits. The acting is good, and in particular, Kiefer Sutherland is great as creepy doctor who adds an artistic touch to the Strangers' experiments. This is a movie worth watching on the big screen and I highly recommend it.