Dr. Edward Pretorius, played by Ted Sorel, is a brilliant scientist who creates the Resonator, a peculiar machine designed to expand the perception of reality beyond the ordinary. His assistant, Dr. Crawford Tillinghast, activates this radical device and is immediately confronted with bizarre and terrifying creatures floating in the air. When one of these entities bites him, Crawford desperately implores Pretorius to shut the machine down. However, Pretorius, completely entranced by the machine’s effects, is lost in what he describes as an "orgasm of the mind," ultimately refusing to comply.
Chaos ensues as Crawford escapes Pretorius' attic laboratory wielding a fire axe, only to be found later by the police—who discover Pretorius' decapitated body—leading to Crawford's arrest for murder. He ends up confined in a psychiatric facility, where he encounters Dr. Katherine McMichaels. Katherine conducts an examination and discovers that Crawford's pineal gland is abnormally enlarged. Believing in his innocence, she decides to revisit the house to witness the Resonator for herself, joined by Detective Bubba Brownlee, who was initially involved in the investigation.
Upon returning, Crawford and Katherine proceed to rebuild and reactivate the Resonator. This leads to an alarming resurgence of the creatures, including a grotesquely transformed Pretorius, who reveals to the trio that another world exists, far more exhilarating than the mundane. In a horrifying moment, when Crawford attempts to touch him, Pretorius’ body disintegrates, provoking Bubba to draw his weapon and fire at him. Crawford is quick to disable the Resonator, resulting in the disappearance of both Pretorius and the creatures.
As morning breaks, the trio discusses their harrowing night over breakfast. Despite Katherine's insistence that the Resonator might address schizophrenia, both Crawford and Bubba are reluctant to activate it once more. They each drift into sleep, nursing headaches, but Katherine, driven by a yearning for the machine's ecstasy, clandestinely reactivates it, unleashing the now grotesque Edward upon them. As chaos unfolds, he makes a gruesome advance toward Katherine, stripped of her clothes, intent on feeding on her mind.
Crawford and Bubba make a frantic descent into the basement to cut the power, only to confront a monstrous worm. As the creature begins to engulf Crawford, Bubba manages to shut down the machine, reviving Crawford and banishing Edward into the unknown. Despite their initial relief, Katherine is consumed by guilt for her reckless actions.
With tensions rising, Bubba advises that they leave the house; however, Katherine insists on monitoring the machine to uncover the source of the creatures. She begins to search through the house, inadvertently discovering Edward's old S&M costumes, and momentarily loses herself in their allure. In a panic, they all rush back to the attic to disable the Resonator once more, but they are attacked by tiny, flesh-ripping creatures, claiming Bubba as their next victim.
In a desperate struggle against Edward, whose form has further grotesquely mutated, he ensnares Katherine and threatens her very existence. Crawford, battling Edward for control, finds his pineal gland extends outward like an antenna. Katherine, exhibiting courage, neutralizes the machine using a fire extinguisher. She takes Crawford back to the hospital, where she faces accusations of insanity following the night's events, landing her under the watch of the nefarious Dr. Bloch.
As chaos ensues at the hospital, Crawford, returned from the dead in a grotesque state, seeks brains to consume. Katherine escapes Dr. Bloch's clutches, ready to confront the Resonator with a bomb attached to it for a fiery conclusion. When confronted by Crawford, who has become a twisted shadow of himself, she narrowly avoids being devoured. Just as Edward’s monstrous form threatens her life, Crawford’s humanity flickers back to the surface when Katherine bites off his overevolving pineal gland.
The climactic confrontation erupts in the laboratory as Edward and Crawford wrestle for supremacy over the mutilated form. Katherine's escape through a window coincides with an explosion that eradicates the attic, leading her to land in a heap, injured yet alive. Surrounded by neighbors drawn by the chaos, she oscillates between terror and laughter, declaring with haunting joy, “It ATE him!”
