Brian Innes is asked by a doting to see his daughter Audrey Page when she comes to Geneva and convince her not to stay at film star Eve Ferrier's villa. Eve has a mysterious past her first husband Hector Matthew's died in a strange accident while the couple was visiting Adolf Hitler at Berchtesgaden in 1939, with no apparent reason he apparently flung himself off a high balcony. Audrey ignores Brian's advice and instead becomes involved with the strange group at the Vila Rosalind. Innes meets with Eve at a creepy nightclub called "The Cave of the Witches" and finds she is carrying a perfume bottle filled with oil of vitriol, apparently to her own surprise. At the villa the next day Eve falls to her death from a high balcony -- and no one was near her at the time. The investigative genius of Gideon Fell joins the mystery to uncover an ingenious murder method and reveal the criminal.