He tunes into a radio frequency by accident which is actually the crew following his actions and preparing for him. The biggest clue is when he bumps into his long dead Dad on the street. With these clues he begins to suspect something very strange and very big is going on. He desperately tries to leave Sea haven but is blockaded at every turn. The technology in this film is awesome, and somehow believable.
Sea haven is a charming little town, complete with a shoreline and beach.
The town is enclosed in a dome and the elements are computer controlled. The computer controlled weather system has a scene, and you get a very good look at the interface, which is a touch-screen soundboard. There are tiny spy cameras in every nook and cranny. Let's talk about those Head Geeks. Both are hunched over computers, or commenting on Truman like subdued Beavis and Buttheads.