16-year-old Mark meets local girl Rachel on the internet, he begins an intense online relationship. He quickly finds that he’s besotted, that he’ll do anything for her, even befriend her awkward, loner brother, John. When Rachel, who is trapped within the grips of a possessive boyfriend, is murdered, Mark and John make plans to avenge her death. Their actions draw the attention of a secret government department as they unwittingly stumble upon an ongoing operation. Soon Mark is recruited to commit a crime that made British legal history.