Early in the 20th century, middle-aged lawyer Fredrik Egerman (Gunnar Björnstrand) and his young wife, Anne (Ulla Jacobsson), have still not consummated their marriage, while Fredrik's son (Bjorn Bjelvenstam) finds himself increasingly attracted to his new stepmother. To make matters worse, Fredrik's old flame Desiree (Eva Dahlbeck) makes a public bet that she can seduce him at a romantic weekend retreat where four couples convene, swapping partners and pairing off in unexpected ways.