David Haller, AKA Legion, is a troubled young man who may be more than human. Diagnosed as schizophrenic, David has been in and out of psychiatric hospitals for years. But after a strange encounter with a fellow patient, he’s confronted with the possibility that the voices he hears and the visions he sees might be real.

A suburban couple's ordinary lives are rocked by the sudden discovery that their children possess mutant powers. Forced to go on the run from a hostile government, the family joins up with an underground network of mutants and must fight to survive.