Scanners - 1981 - written and directed by David Cronenberg, starring Stephen Lack, Jennifer O'Neill, Michael Ironside, and Patrick McGoohan.

Why are you such a derelict? Such a piece of human junk? The answer's simple. You're a scanner, which you don't realize. And that has been the source of all your agony. But I will show you now that it can be a source of great power....