Truman Brubank lives happily in a small, peaceful and beautiful town called Seahaven. He has a quite good job, a nice wife, and basically a happy life, until he starts to suspect that his life is a fake.
The town Seahaven is really an extremely big filmstudio (the Great wall of China and this dome are the only things that can be seen from space), full of cameras, in which the world's most famous reality show, The Truman Show is recorded and broadcasted to the entire world.
The main character is Truman, who doesn't know about that; everybody else are stunts and actors. Truman was adopted by the film company right after his birth, they raised him with false parents, and since Seahaven is surrounded by water and they don't want Truman to get off the island, they managed to make him hydrophobic by drowning his 'father'.
One day mysterious things start to happen - a big lamp falls from the sky; Truman hears on the radio that his actions are being reported; a total stranger calls him by his name; he sees actors change dress in a bank etc. Then he desperatedly wants to break out from Seahaven, but he is very well guarded.