"Doorway to Nightmare"
A couple, Douglas Holt and Melissa Mann visit Madame Xanadu's shop for a Tarot card reading. Madame Xanadu predicts a dismal future for Melissa unless she abandons her scientific pursuits.
This advice is vehemently discarded by Melissa as she leaves angrily. Along with her close colleague, Hampton Hill, Melissa is working on a project to unlock the gateways to other dimensions.
They succeed in opening a portal for Demons to swarm all over them. Douglas takes immediate action, smashing the control panel of the gateway device. Melissa shows her gratitude by asking Douglas to accompany her to dinner that night.
The evening ends with a romantic tryst, but three days later Douglas is back at Madame Xanadu's relating a sorrowful tale. The next night Douglas had been out with Melissa, she had thrown herself at a total stranger and absconded with him.
When Douglas tried to confront her about this aberrant behaviour, Melissa goes wild, smashing equipment and attacking Douglas. Hampton Hill suggests she be admitted to Bellevue Hospital for psychiatric tests.
Madame Xanadu suspects this is a case of Demonic possession. She, along with Douglas, visits Melissa at the hospital. As they perform an exorcism, the Demon that was controlling Melissa ejects from her body in an attempt to possess Douglas. Madame Xanadu springs into action, containing the Demon essence in a crystal jar.