Frenzy (1971)

A woman murders her disabled husband and informs his brother (with whom she is having an affair), but she realizes she has misdialed and accidentally confessed her crime to a stranger. The caller attempts to blackmail her, but when he tries to rape her she kills him in the struggle. Worse still, her doctor and lover inform her to say nothing because her husband has been dead for eight months and everything that has happened she has imagined.