The Little Girl Who Fell from the Tree (1998)

Set in Berlin, this film follows Lisa, a mysterious young lady who moves into an apartment, next door to newlyweds. Domesticated bliss is shown to be somewhat lacking for this couple, as these seemingly normal neighbors slowly betray odd characteristics... Jenny suffers from mental illness (perhaps exacerbated by abuse as a child) and Ben is a frustrated husband who deals with his wife's illness by becoming a workaholic. Into this unhappy couple's lives steps Lisa, who finds a needy friend in Jenny and a seductive game in snagging the wanting Ben.