Back when Mike Lowrey was in the police academy, he was pulled out to go on an undercover mission, chosen in part because nobody would know him. He became a driver within the Aretas drug cartel, and it was there he became acquainted with Isabel. It turns out the pair became much more than simply friends, leading Mike to have to make a choice when the time came for the police to move on the cartel. He chose to let Isabel get arrested, but the other shoe drops when we learn that Isabel went into prison pregnant, and the child she gave birth to, the one that’s been trying to kill Mike all this time, is his son.