Pinter's play tracks the course of an affair, but it does so backwards: it opens with a meeting between the two lovers some years after the affair ended; it finishes with the first erotically charged encounter between the two, nine years earlier. The performers have to chart the stages in the affair, discarding the layers of guilt, to become the younger, fresher.

Betrayal is a play written in 1978. Critically regarded as one of the English playwright's major dramatic works, it features his characteristically economical dialogue, characters' hidden emotions and veiled motivations, and their self-absorbed competitive one-upmanship, face-saving, dishonesty, and (self-)deceptions.
Betrayal was inspired by Pinter's seven-year affair with television presenter Joan Bakewell who was married to the producer and director Michael Bakewell, while Pinter was married to actress Vivian Merchant. Although the affair was known in some circles, it only became public knowledge after it was confirmed by Pinter in Billington's 1996 authorised biography, which was further confirmed in Joan Bakewell's later memoir The Centre of the Bed.

Betrayal received the Laurence Olivier Award for Best New Play in 1979.