Valentine Pescatore is a rookie Border Patrol agent, just trying to survive the Line. Until he pursues a suspect across the border into Mexico, and finds himself in serious trouble. Isabel Puente is a beautiful US agent investigating a powerful Mexican crime family. She offers Valentine a chance - if he works with her as an undercover agent she'll make his problems go away. Over the border in Tijuana, anti-corruption chief Leo Mendez is working to bring criminals to justice. In a city where anyone can be bought, he's made enemies on both sides of the law. All three have the same aim: to bring down the cartels.