Roberto, a drummer in a rock band, starts getting strange phone calls and is being followed by an unknown stranger. Dario Argento wrote and directed the 1971 giallo film Four Flies on Grey Velvet. Roberto follows him to an empty theatre, where he discovers the stranger has produced a knife but is murdered in the scuffle. Meanwhile, a third individual is photographing the incident from a gallery. Robert has been blackmailed, but the blackmailer has not wanted money. The film was made in Italy and France by the Rome-based Seda Spettacoli and the Paris-based Universal.