La Maison sous les arbres (1971)
Directed by René Clément

Film Synopsis

Philip, a young mathematician, and his wife Jill have been living in France with their two young children, Patrick and Kathy, for two years.  Not so long ago, they were once leading a happy life in their native America, before events drove them to move to Paris, their adopted home.  Recently, the couple's relationship has come under increasing strain as a result of a feeling they both have of being threatened.  Their anxieties seem to have no rational basis and it looks as if the couple are succumbing to a shared paranoid delusion.  Their worst fears are suddenly borne out when their two children are kidnapped.

As he begins his investigation into the children's disappearance, Inspector Chameille soon begins to suspect that Jill may have killed them whilst suffering from an attack of nervous depression.  Meanwhile, Jill's suspicions are directed towards her babysitter Lucie, whose behaviour has struck her as being somewhat bizarre.  Philip is then approached by a powerful secret organisation he once had dealings with, and before he knows it he is being coerced into becoming an industrial spy.  The only person he feels he can rely on is his friend Cynthia, but she isn't as blameless as she appears...