1960s horror following workaholic scientist Dr. Henry Jekyll (Paul Massie) as he embarks on an experiment which turns him into Edward Hyde. Jekyll's wife, Kitty (Dawn Addams), has no hope left for their marriage and is having an affair with Paul Allen (Christopher Lee), an old aquaintance of Jekyll's. When he transforms into Hyde, Jekyll becomes friends with Allen, who soon finds out that Hyde is violent and arrogant. At Hyde's request, Allen takes him around London's seedy night life, where Hyde meets and becomes involved with working girl Maria. Then, disguised as Hyde, he attempts to beguile his wife, but will he succeed?