Charley Banks is an ordinary English major at a prestigious middle-American university, with friends, a part-time job, a long-term girlfriend, and loving parents.  For fun and for an interesting experience – and to get a bit of extra money – he takes part in a seemingly unremarkable and benign experiment in the Neuroscience Department, testing a new version of a trans-cranial magnetic stimulator.  After the initial test, however, Charley has a severe seizure in the MRI machine.

He awakens in the hospital to discover that now, with just a touch, he can extend his mind into others, replacing their consciousness with his own, operating their bodies, having access to their personalities and memories.  Initially this control lasts only while he is touching them, but soon the power grows, and Charley finds himself able to control others even when they are no longer in contact.  He also learns that he can control more than one person at a time, and that each new person he incorporates can extend him further into others.

Thrilled by his new ability, Charley determines to keep it a secret, at first even from his girlfriend, while he explores its implications and its limits, if there are any.  Though he thoughtlessly reveals something of the power to the professor who ran the initial experiment, the professor does not believe him.

It soon becomes clear, however – or it would if anyone knew of it – that something else has changed in Charley, beyond his paranormal power.  For in his use of his new ability, he quickly begins to do increasingly terrible things…especially once he learns what happens when someone dies while he is controlling them.