In 1960, Billie Valentine is a young housewife living in a sleepy Massachusetts suburb, treading water in a dull marriage and caring for two adopted daughters. Summers spent with the girls at their lakeside camp in Vermont are her one escape - from her husband's demands, from days consumed by household drudgery, and from the nagging suspicion that life was supposed to hold something different. Then a new family moves in across the street. Ted and Eva Wilson have three children and a fourth on the way, and their arrival reignites long-buried feelings in Billie. The affair that follows offers a solace Billie has never known, until her secret is revealed and both families are wrenched apart in the tragic aftermath. Fifty years later, Ted and Eva's son, Johnny, contacts an elderly but still spry Billie, entreating her to return east to meet with him. Once there, Billie finally learns the surprising truth about what was lost, and what still remains, of those joyful, momentous summers.