A US marshal and her prisoner are gunned down outside of London's Heathrow Airport just as the prisoner is to testify against the head of a violent animal-rights group. Leeds Detective Sergeant Keen Dunliffe doesn't seem like the right man for the case, except that he has the undercover experience and knowledge of Yorkshire, the terrorists' backyard. He's ordered to head up a sting operation with Rachel Colver, an inexperienced police constable, who may have personal ties that will help her infiltrate the animal-rights group. However, Keen is worried about a plan that puts Rachel in obvious peril. As the two hunker down to work the case from the inside, brutal extremists and police politics collide, involving murder, intimidation, smuggling, and blackmail with lethal consequences.