Dr. Ernest Sovac, a brilliant but morally ambiguous scientist, becomes embroiled in a dangerous experiment involving brain transplantation. Dr. Sovac's close friend, Professor George Kingsley, suffers a severe injury during a car accident orchestrated by mobster Red Cannon. In a desperate bid to save his friend's life, Dr. Sovac transplants part of Cannon's brain into Kingsley's body. As a result, Kingsley begins exhibiting dual personalities: his own and that of Cannon. Sovac soon realizes that Cannon hid a fortune somewhere before the accident, and he endeavors to use Kingsley's second personality to locate it.

As Kingsley struggles with his conflicting identities, the criminal underworld learns about Cannon's new condition and grows increasingly suspicious. The duality within Kingsley leads to chaos and tension, as Sovac becomes more willing to cross ethical boundaries for personal gain. The evolving personalities inside Kingsley result in unpredictable behavior, causing friction with those around him and drawing the attention of law enforcement. As events spiral out of control, the lines between morality and ambition blur for the characters involved, culminating in a series of dramatic confrontations and moral reckonings.