Jerry is a literary agent; Emma runs an art gallery; Robert is a publisher. Emma and Robert are married and Jerry is Robert's best friend, but Emma and Jerry have had a seven-year affair. The play opens with Emma and Jerry meeting for lunch in 1977, two years after the affair has finished and by a brilliant device the relationship of the three is traced backwards nine years to the evening when it all began.

Critically regarded as one of Pinter's major dramatic works, Betrayal is famously inspired by his clandestine extramarital affair with BBC Television presenter Joan Bakewell, which spanned seven years, from 1962 to 1969. The plot integrates different permutations of betrayal relating to a seven-year affair involving a married couple.

First presented at the National Theatre in 1978, the original cast featured Penelope Wilton as Emma, Michael Gambon as Jerry, Daniel Massey as Robert, and Artro Morris as the waiter; Wilton and Massey were married at the time. It was designed by John Bury and directed by Peter Hall.