Vincent and Cat face the fact that they've lost control of their secret and may have to go on the run. Vincent also realizes that he needs to face his past; and Cat worries about what they may lose.
Vincent undergoes a series of tests arranged by the mystery buyer in order to not be exposed; and Cat, JT and Heather try to exonerate Vincent.
Vincent and Cat strive to return normalcy to their lives despite the threats posed by a beast bounty and DHS manhunt; and Tess takes a risk by shielding Vincent from a reporter.
Vincent goes undercover with an operative whom Cat learns is an assassin; and Cat tries to prove to DHS that she can still be trusted.
Vincent and Cat regroup in their effort to bring down the beast hunters. To that end, Vincent tries to infiltrate a private army while Cat attempts to obtain information at work while hoping no one discovers her ulterior motives.
Vincent and Cat learn that another nemesis is out to get Vincent; and their relationship is endangered when they wind up on opposite sides of the law.
When Vincent and Cat are forced into hiding due to his being someone's target, he wonders what life would have been like for her without him in it—and gets a glimpse of just that.
Cat investigates who's after Vincent and suspects that she may be pregnant. In other events, Vincent follows a lead that puts his life in jeopardy; and J.T. is kidnapped in a case of mistaken identity.
Cat and Vincent's newlywed life is upended by lurking danger and they soon find themselves in the fight of their lives.
Cat and Vincent hunt a black marketeer of beasts; and try to protect an heiress whose identity was revealed.
In the Season 4 premiere, Vincent and Cat's wedded bliss is short-lived when J.T. brings them the news that someone is trying to expose the identities of beasts.