When US Marshal Jay Stonewalker sees a possible terrorist comment in a chatroom frequented by anti-government radicals suggesting a nuclear threat to New York City, specifically the Waldorf Astoria Hotel, he can't get it out of his mind. Against his boss's orders he heads off to NYC to investigate on his own time. While there he follows a suspicious character into a secluded recess of the New York Subway system and foils what he believes is the terrorist event. In a shoot-out with his suspect he's wounded and calls the NYPD for backup. When he sees NYPD Detective KC Daviau and other uniformed officers slipping into the darkness from the subway platform he's relieved, but to his surprise he's met with resistance and disrespect by Detective Daviau. Against his objections, KC takes custody of the evidence and leaves the scene. When Jay asks an officer if she is always that way he's told that, "Since her parents died, she's been... let's say... a little cold." When they are assigned to work the case together, KC's icy exterior soon begins to melt away as they begin to fall for each other, but KC has to hold back. She has a dark secret and knows he can't ever know her truths because if he did he would hate her just as she hates herself for what she's about to do.