While on the run from their Medusan pursuers, Adam and Shem take over a castle. Fulvia and Octavia demand that the authorities on Earth hand over their escaped servants, but are surprised to learn that the policemen on our world refuse to submit to their every whim. Undetered by this, the two Medusan leaders take Professor Evans' assistants, Liz and Rudi, as hostages. They then prepare to unleash the full force of a fear-inducing Medusan weapon known as the Nightmare Cannon upon Adam and Shem.