Giorgio D'Amato agrees to meet his friend Enrichetta at Edmondo Parisi's mansion, but upon his arrival, he discovers the model has been stabbed to death with a pair of scissors. Her attendance at the villa had been requested by the paralyzed and neurotic Parisi, inventor of a technology that enables him to photograph his thoughts. Other guests include Eleonora, Parisi's lesbian wife; Alberto, the omnipresent butler; and Lucia, the unrestrained maid. The only person who appears to be normal is Sara, Edmondo's niece, who enlists D'Amato's assistance in locating the murderer. Soon after, the strange hand strikes again, this time targeting Lucia...