A neurosurgeon with a cheating wife takes an amnesiac into his home and conditions him to believe that the cheating wife is his own and to take the "appropriate" action.
Someone Behind the Door is a 1971 French crime-drama film directed by Nicolas Gessner. In the UK, it was twice retitled as Two Minds For Murder and Brainkill. It is based on a novel by Jacques Robert. The film was shot on location in Folkestone, England.