Diabolique - Ending Explained

The central, brilliant twist of "Diabolique" is the revelation that Michel Delassalle was never murdered. The entire drowning was a meticulously staged fake-out, orchestrated by Michel and his mistress, Nicole Horner. Their true plan was not for the two women to kill the man, but for the two lovers to murder the wife, Christina. Knowing about Christina's severe heart condition, they concocted the elaborate 'haunting' to literally frighten her to death.

Every strange event that torments Christina is part of their cruel design. The body disappears from the pool because Michel simply got out and walked away. The suit is returned from the dry cleaner because he was never dead. The boy, Moinet, really did see Michel alive. The 'ghostly' face in the school photograph is just Michel. The climax reveals the full extent of their diabolical plan: as a terrified Christina flees through the dark school, she is confronted by Michel, who rises from a full bathtub wearing white contact lenses to appear dead. The shock induces the fatal heart attack they intended all along. In the immediate aftermath, as Michel and Nicole embrace and congratulate each other on their perfect crime, they are overheard and caught by the quiet Inspector Fichet, who has been observing all along, ensuring their plot ultimately fails.

A final layer of ambiguity is added when the student Moinet claims Christina gave him his slingshot back after she had died, leaving the audience to ponder whether her spirit has returned or if it is merely a child's fantasy.

The most debated element of "Diabolique" is the final scene. After the villains have been caught, a young student, Moinet, is seen with his slingshot. When a teacher asks how he got it back, the boy claims that Christina returned it to him. This leaves the ending open to several interpretations:

• The Supernatural Ghost Ending: The most straightforward interpretation is that Christina's ghost has returned. Given her devout faith and unjust death, her spirit lingers to perform a final act of kindness for the boy. This reading pushes the film from a psychological thriller into the realm of the supernatural, suggesting a form of spiritual justice beyond the capture of the murderers.
• The Ambiguous Psychological Ending: Another view is that the boy is simply lying or imagining it, as children do. This interpretation keeps the film grounded in its grim reality. The teacher dismisses the boy's claim, representing the adult world's refusal to believe in anything beyond the rational. The final shot is simply a final, unsettling question mark, a last touch of ambiguity from Clouzot that leaves the audience in a state of unease.
• The Ultimate Trick Ending: A more complex, though less common, interpretation suggests that Christina faked her own death, somehow anticipating and outsmarting her would-be killers. According to this theory, she knew about the plot and played along, perhaps with the detective's help, to trap them. This would make her the ultimate manipulator. However, this reading is contradicted by the visual evidence of her terror and Michel checking her pulse.