Sulu, Scotty and Jackson explore Pyrus VII, and then Jackson calls the ship, "one to beam up". He materializes dead, and a sepulchral voice threatens Kirk, saying his ship is cursed! Beaming down, Kirk discovers his men enslaved by strange aliens, who have created a Gothic castle and other artifacts straight from Halloween. But their power and threat are real - they are from a place so alien, that the sensations of this universe are intoxicating. If not stopped, they pose a grave threat to the Federation.

Enterprise sends a shuttlecraft to retrieve Federation Commissioner Nancy Hedford, who suffers from Sakuro's Disease, so that she may be treated. The craft is pulled off course and lands on a small planetoid, where the crew discover the systems will not work. They also discover a man, apparently living alone there - or, is he? He seems to from time to time commune with an energy cloud, the alien being responsible for forcing the shuttlecraft down. It means for the crew to serve as companions for the man - forever.