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.

Vincent moves in with Cat which forces them both to address the rapid changes in their relationship while they investigate a shocking new lead in their hunt to track down who is behind the super-human experiments. JT tries to impress Tess' brothers and discovers that there may be some side effects to the medicine he received from Agent Thomas. Meanwhile, Heather returns to town with a surprise announcement.

Captain Ward passes on the order to hand the official investigation into the double agents murder over to Homeland Security agents Bob and carol, a couple. Supposing only their inside super-beast project information can crack the case, Vincent and Cat agree to keep on it and attempt teaming up with the couple. As Bob warned, 'marriage planner' Heather goes overboard, as if recuperating her canceled dream wedding. Ballistics help point to drug cartel lord Julio Espinosa, whom the two duos agree to take on. Vincent duly gets suspicious, only minutes before betrayal strikes on his home boat. Written by KGF Vissers

After a quiet period, Vince accuses Cat of looking for cases where there are none, she him of avoiding their relationship issues and burying himself in medical work, actual forced to catch up in hospital. They agree to attempt couples counseling but can't tell Dr. Glenroy the 'beatly' truth. When terminally ill billionaire Zalman suspiciously 'finds' the only compatible donor heart used when he needs it, they investigate, but it's stolen and abandoned after the thief is murdered, the trail leads to his wife. It's diagnosed beast-experimentally serum-treated, but JT tries the antedate on it he works on to neutralize his own beastly regeneration and unknown powers. Written by KGF Vissers

Once again, Vince hopes for a normal life while Cat can't help waiting for another Beast case, despite Tess's selfish wining about her captain career and assigning Cat a rookie as new NYPD partner. J.T. takes painfully risks in an attempt to find an antidote for the serum, fearing his growing powers might ultimately turn him into a beast. Cat is convinced to spot fake Home Security agent Carol, but can't pin her down, while indeed she and Bob are hell-bet on redeeming themselves for the failed double assassination by testing Vince, separated from Cat, as ideal guinea pig Beast. Vince is lured into tracking down and saving innocent Eddie Daniels, then darts-tranquilized, J.T. finds him and resorts to a desperate risk. Written by KGF Vissers

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.

Vincent and Cat decide to get married and invite both family and police to the church, determined not to cancel again. Julianna Keaton escapes and abducts Cat during her limousine ride to church, but Vincent comes to the rescue just in time. He lets Tess talk him out of wisely canceling when the NYPD is informed that bloodthirsty super-beast Liam has arrived from London, so the church becomes a carnage site. Written by KGF Vissers

The wedding hasn't ended the dispute whether the hunt for (super)beasts and their creators should dominate the couple's lives. Cath openly opts out, even makes Tess tell Captain Ward the case must be officially turned back to federal agencies for Interpol collaboration. But the Beast-related problems keep coming. Although dumped by jealous Tess, JT explains to her the relevance of Cat's ancestors' beast hunt experience, and his fear giving it up would mean her generation's death. Written by KGF Vissers

Cat and Vincent find information about Patient X that could help them find Liam; Tess works with J.T. to make sure he is serum-free.

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.

Vincent and Cat must work together to defeat Liam, who will do whatever it takes to expose Vincent as a beast.