A young couple become embroiled with the personal problems of another couple on a yacht moored off Sicily during a turbulent weekend of fun, games, sex games, betrayal, spouse abuse, and murder.
A doctor kills his girlfriend when he accidentally causes her to fall onto an ornamental flower which has metal spikes. He disposes of her by chopping up and then dissolving her corpse. The woman's sister accuses the doctor and an investigation begins. In the meantime, a second woman is killed and the doctor begins to receive metal petals through the post.
