Robert and Alice are 15-year-old twins, who live in a big house in the country. The school year is drawing to a close, and a hot summer begins. For Robert, everything in his life feels wrong: his family, his friends, particularly his embarrassing sister Alice. Then Nick appears, dazzling, devil-may-care, extraordinary, offering an unexpected friendship. Robert is thrilled by the attention, and his sense of dislocation with the rest of his life grows. In the suffocating heat, heavy with boredom and frustration, he hangs about waiting for Nick who turns up only occasionally, but always promising great things. He begins to encourage Robert to give in to the spiteful part of his nature: letting bulls into a field to frighten his father's friend, setting hay bales on fire, and even killing a baby bird.

As the summer wears on, an old homeless man is occasionally seen roaming around the farm, giving all who come across him an inexplicable feeling of revulsion and dread and a sense of mounting foreboding. The conflicting fascination and fear of Nick draw events towards their climax. It is only Alice who clearly recognises Nick for what he is, and can hope to save her brother ...