The reclusive, eccentric scientist Oscar Collins (Jack MacGowran) has two next-door neighbours: a pop photographer (Iain Quarrier) and his girlfriend/model Penny Lane (Jane Birkin). Discovering a beam of light streaming through a hole in the wall between them, Collins follows the light and spots Penny modelling for a photo shoot. Intrigued, he begins to make more holes as days go by and they do more photo sessions. Oscar gradually becomes infatuated with the girl, and feels a part of the couple's lives, even forsaking work to observe them. When they quarrel and the couple splits, Penny takes an overdose of pills and passes out, but Oscar comes to her rescue.