Several weeks have passed since their epic defeat of Gabe, and Cat and Vincent are finally able to begin a new, "normal" stage in their lives. Unfortunately, "normal" isn't in the books for him, as confirmed by the two FBI Agents trying to recruit him.
Cat and Vincent take their relationship to a couples counselor when Cat dives into her work and suspects a wealthy transplant recipient of being involved with the mysterious experiments on innocent people in the city.
JT throws Vincent a surprise bachelor party. Unfortunately, it is interrupted by a mysterious sniper with his sights set on putting a stop to Vincent and Cat's interference with the super human experiments. Cat's family comes to town for a bridal shower arranged by Heather but Cat is distracted by having to visit her imprisoned father to ask for his help.
When an unstoppable assassin hunts down Cat and Vincent, they attempt to lure him out of town and away from their loved ones with the ruse that they plan to elope. Meanwhile, tired of being under police protection, JT asks Tess to help him track down a lead while a distracted Heather attempts to focus at her new job.
In a surprising turn of events, Vincent agrees to help Liam on a mission to retrieve evidence that could expose them both. Meanwhile, a suspicious Cat discovers something about Liam's family history and must warn Vincent before it is too late.
Liam's shocking history makes Cat delve deeper into the Ellingsworth family, where she learns of their tragic past. Vincent and Cat realize that they will need to use their secret weapon if they want to take Liam down. Meanwhile, JT has a theory about how to save himself but it involves none other than Liam.