lose friends Rupert Birkin (Alan Bates) and Gerald Crich (Oliver Reed) begin romances with siblings Ursula (Jennie Linden) and Gudrun Brangwen (Glenda Jackson). After the couples wed, they take a joint honeymoon to Switzerland, where things begin happily -- but they become increasingly complicated as the trip continues. Rupert and Ursula are determined to stay faithful to one another, while the aloof Gerald and the eccentric Gudrun turn to infidelity and sexual exploration.

Overview from themoviedb.org