Jack, who is fifteen, is just getting used to his parents' divorce when his father takes him out on a boat ride one afternoon and stops in the middle of the lake to explain that the new love in his life is a male, and that he is, and has very likely always been, gay. The shock sends Jack through several levels of reaction, from revulsion to hostility to fear of social ostracism, to grief at the alienation he assumes is now inevitable between him and a father he has loved.
In fact, people at school do find out and he finds the word "faggot" painted on his locker. Discovering that a girl in his class has a gay father in the same social circle as his own puts a slightly new light on his predicament, and gradually Jack comes to a place of peace in learning that he can love his dad without either judging or condoning his homosexuality, and can look forward to an adult life of his own in which there will be complex choices of his own to make, as there have been for his parents.