Frederick Clegg (Terence Stamp) is a lonely, unbalanced young man who stalks a pretty and young art student, Miranda Grey (Samantha Eggar). One day, after following her in his van, Frederick kidnaps and chloroforms Miranda, locking her in the windowless stone cellar that he has prepared with a bed, some furnishings, and an electric heater. Frederick is a butterfly collector and treats Miranda as if she is one of his specimens.