Just before a London symposium to discredit devil-worshipping cult leader Julian Karswell (Niall MacGinnis), the mysterious death of conference organizer Henry Harrington has left American psychologist John Holden (Dana Andrews) in charge of the proceedings. Though Holden refuses to believe that his predecessor's bizarre death was the result of a curse, Harrington's niece, Joanna (Peggy Cummins), is certain that her late uncle's notes contain evidence proving Karswell has satanic powers that he is all-too-willing to use against those who threaten to expose him. But when Holden connects his own strange sensory disturbances to an ancient parchment containing a curse like the one that killed Harrington, he and Joanna must find a way to return it to Karswell before it's too late!