Enraged by his wife's infidelity, a dead man's spirit returns as a vengeful demon which takes possessed his daughter after she becomes involved in witchcraft. The girl turns into a drooling, obscenity-spewing, homicidal maniac, prompting a call to be placed to a expert in demonology who could possibly purge the demon from her body. Spanish horror favorite Paul Naschy both wrote and stars in this Euro-horror take on THE EXORCIST, which had taken the world by storm two years prior.