Three months after Vincent Keller was abducted by Muirfield, Detective Catherine Chandler is reunited with him - but not in the way she planned. He's changed: his scar has disappeared, his memory has been wiped clean and he returns as a supercharged beast on a mysterious mission.
After getting stonewalled by Cat in his quest to track down a suspected beast, Gabe enlists Vincent's help, but Vincent quickly takes matters into his own hands. Unfortunately, the beast has an advantage over Vincent that requires Cat's help, in addition to the help of someone else who opens up old wounds from Vincent's past.
Cat gets a blast from the past as she attends her high school reunion, where she uncovers more of her past than she ever anticipated. Meanwhile, Vincent meets up with one of his old military buddies who is hiding a very dangerous secret.
Cat confronts her birth father about the mysterious role he's played in her life, while Vincent has to neutralize a high-profile beast. In the process of doing so, Vincent finds himself rescuing Tori, a damsel in distress, who may be the key to completing his mission.
After Vincent's life is endangered, Cat decides they should spend Thanksgiving with her father in order to get information on Vincent's missions. However, when Gabe and Tori join the festivities, true feelings are revealed and secrets are outed. Meanwhile, J.T. and Tess get a surprise while they celebrate Thanksgiving together.
Vincent and Cat find themselves at odds on how to deal with Agent Reynolds, which forces Vincent to wonder if he is more beast than man. Cat makes a drastic move that will forever change her relationship with Vincent.
In order to prevent Vincent from further injuries, Cat tranquilizes him and steps in to help protect Tori when her life is threatened, revealing a new, unexpected mystery. Vincent's stubborn attempt to intervene leads to life-changing consequences. Meanwhile, Gabe and Cat to grow closer.
Vincent goes on a national talk show to reveal that he is still alive. Then, determined to learn more about his beastly origins, he tries to find men who attacked JT. Cat dives into an undercover case for FBI Agent Dana Landon, hoping it would help her get over her break-up with Vincent. Cat and Vincent end up face-to-face in the middle of a heist.
A group of criminals looking to steal a rare necklace in Tori's possession takes Cat, Tori and Tess hostage at the precinct, leaving Vincent as their only hope for help. Vincent is forced to make a decision since helping could reveal his true identity to the entire force.
Cat and Vincent must work together to save J.T. when he gets kidnapped, while Tori attempts to intervene, with fatal consequences. Meanwhile, a stranger from FBI Agent Dana Landon's past is rescued along with J.T., and might have some insight about Vincent's beastly past.
After Gabe's fake funeral Tess follows Sam in an attempt to figure out what he is planning to do next. Vincent decides to play 'beast' cold turkey with Cat while Cat is trying to make her relationship with Gabe work.
Feeling pulled between her current boyfriend and her ex, Cat has to decide between Gabe and Vincent. While Cat and Vincent work together to save Sam's latest victim, Cat's decision gets complicated when she and Vincent find themselves in a compromising situation.
Vincent is arrested for murder. Cat, J.T., Gabe and Tess try to keep him from "beasting out" in jail until they can get him released. They wonder who took evidence to the police. Tess and J.T. aren't successful at keeping their night a secret.
Gabe initiates a city-wide manhunt for Vincent and sets up a command post at the 125th. After discovering Cat has disappeared, Tess enlists J.T.'s help to find Vincent so he can track her. Cat's kidnappers identify themselves as FBI agents, desperate for hers and Vincent's help to save a fellow agent that has been taken by terrorists. Cat doesn't believe them and escapes, just as Vincent arrives to save her. They agree to help rescue the FBI agent, in exchange for Vincent's exoneration of Curt Windsor's murder. However, things do not go according to plan after the ...
The noose tightens as Gabe uses all available NYPD resources to hunt Vincent. Cat and Tess are both suspended for helping Vincent elude capture. Heather arrives at the worst possible moment with big news. Fighting back, Cat and Vincent independently unearth evidence linked to a cold case that implicates Gabe. A desperate Gabe begins to unravel, leading to disastrous consequences.
After their attempts to convict Gabe fail, Agent Knox enters Vincent and Catherine into Witness Relocation, but their safety in suburbia is short-lived. Gabe sets a trap for Vincent, leading to a dramatic confrontation with Tess and J.T..
Desperate to start over with Cat, Gabe tries to woo her by taking her on a romantic date. Cat accepts the invitation in exchange for Gabe calling her reporter friend Beth off Vincent's trail. However, after things don't work out between them, Gabe takes the serum to get his beast powers back. Meanwhile, Tess helps organize Heather's bachelorette party and Vincent is exonerated.
Gabe goes after Vincent's friends in order to get his attention, lure him out and kill him. Cat studies the journals of her ancestor Rebecca Reynolds, trying to figure out a way to stop Gabe and protect Vincent at the same time.