The book loosely chronicles a summer on Fire Island shared by three affluent but troubled adolescents who become increasingly cruel and hedonistic as they experiment with drugs, sex, bizarre social pranks and alcohol, leading them to eventually commit a heinous act against a companion of theirs.

The boys are enamoured with the physically-attractive and fun-loving, hedonistic Sandy and their meeting quickly becomes an intense friendship during which the trio consume beer and share deep secrets about one another.

Their affluent urban parents, on vacation in the nearby cottages, largely ignore them and engage in their own hedonistic pursuits; Sandy confides in the boys that her stepfather, a man nicknamed "Snow White" for his pallid skin, molested her when nobody was looking and made lecherous remarks at her.

On a rainy day, after partaking in the use of marijuana and getting high, Peter develops a crush on Rhoda despite her prudishness and Sandy, learning that Rhoda's mother died in a drowning incident while swimming, decides to make the awkward girl her project by introducing her to more liberal concepts and buying her a bikini to replace the "creepy" modest one-piece bathing suit that she had been wearing previously, which David and Peter believe looks like a bathing suit that an elderly woman would wear.

Rhoda, who had bitten Sandy's hand the prior night in an attempt to break away from her and help Anibal, finally decides to explore the forest with the other teens due to the hot, sticky weather.

The sequel, set at a ski lodge, reveals that all three of the teens are dysfunctional and mentally-unstable as adults, with Peter regularly seeing a psychiatrist who tries to aid him in coming to terms with the sexual violation of Rhoda (who has cut off contact with the trio).

Burlington Free Press considered Come Winter "an unforgettable exploration into the nature of evil... and a brilliant... dazzling portrait of young sociopaths at play", while The Los Angeles Times described it as a "chilling, fascinating novel".

[2][3][4] Last Summer explores themes of hedonism, cruelty, friendship, adolescence, sexuality, human curiosity, the division between liberal and conservative values, parental neglect, violence and bullying.

The characters engage in increasingly cruel, abusive behaviour as the summer continues and despite coming from wealthy families, they struggle to find an outlet for their own frustrations, curiosity and burgeoning sadism.