One night in Britain, electronic devices stop working briefly and a strange fog. A man returning from a party hits a strangely dressed man on the road. When he is taken to hospital they find he may not be totally human. With two more aliens on the loose the hospital finds itself under siege inside a force field. The captured alien tells stories of prisoners and a cruel society - however which of the aliens are really the threat?
This is a very simple sci-fi film. To set it in context I watched it with Species 2. Now Species 2 had a huge budget and plenty of special effects, whereas this didn't have any - it's aliens are basically Asian actors and actresses rather than big rubbery effects. The story is very effective and it manages it by never fully playing all it's cards. We're told several stories from the different aliens and it's not right until the end that the truth is revealed. It's not fantastic, but it's a quite good story that gets more dramatic when the hospital is encased in a force field.
The main reason the film succeeds is it's production and direction. The direction draws menace from shadows and innocent everyday items and adds a great tone to the film that special effects wouldn't have done. The production adds to this - the use of music is excellent - for example near the start a military unit is watching a radar screen with dramatic music, when the radar cuts off so does the music - the silence being eerily effective.
The weaknesses are mainly around the aliens - they're not great actors and it shows when they have to do any length of talking. Other than that it's perhaps a little too slow and simplistic for modern audiences.
Overall it's a very atmospheric thriller that makes up in mood what it lacks in special effects.