Catherine “Cat” Chandler is a smart, no-nonsense homicide detective, who is haunted by her own tragic past. When she was a teenager, Cat witnessed the murder of her mother at the hands of two gunmen. Cat would have been killed too, but someone – or something – saved her. No one has ever believed her, but she knows it wasn’t an animal that attacked the assassins…though it was strange and terrifying, it was human.
Years have passed, and although she thinks about her mother every day, Cat is now strong and confident, a capable police detective working with her equally talented partner, Tess Vargas. The two women make a good team, and have become close friends while working on countless homicide cases under the supervision of their tough-but-fair boss, Joe Bishop. Cat has also become close to another co-worker, the medical examiner Evan Marks, and they’ve developed a fun, flirtatious relationship that could easily turn into something deeper – if Cat would let that happen. However, much to the concern of her younger sister, Heather Chandler, Cat’s romantic inclinations tend toward bad boys.
While investigating a new case Cat and Tess discover fingerprints that lead to a handsome doctor named Vincent Keller, who was reportedly killed by enemy fire while serving in Afghanistan in 2002. Digging deeper, Cat learns that Vincent is actually still alive. For mysterious reasons that have forced him to live outside of traditional society, Vincent has been in hiding for the past 10 years. With the help of his childhood friend J.T. Forbes, Vincent has been able to guard his terrible secret – when he is enraged, he becomes a terrifying beast, unable to control his super-strength and heightened senses. Cat is stunned when Vincent admits he was the “animal” who saved her the night of her mother’s murder. Vincent doesn’t admit the whole truth – he is emotionally tied to Cat and has been watching over her for years.
Cat agrees to protect Vincent’s identity in return for any insight he may have into her mother’s murder. Thus begins a complex relationship between Cat and Vincent, who understand that their connection is extremely dangerous for both of them. Cat’s secret obsession with Vincent puts a strain on her relationship with everyone around her, and Tess is especially troubled by the feeling that Cat is keeping something from her.
Catherine Chandler, played by Kristin Kreuk, is a smart, no-nonsense homicide detective. When she was a teenager, Catherine witnessed the murder of her mother at the hands of two gunmen. Catherine would have been killed too, but someone - or something - saved her.
When a rising young ballerina mysteriously falls to her death, Vincent (Jay Ryan) senses that the understudy, Victoria (Elizabeth Blackmore), is hiding information about the dancer’s murder. Cat (Kristin Kreuk) and Tess (Nina Lisandrello) discover that the victim tried to file a police report for an assault. Meanwhile, Cat seeks out Vincent’s help to decipher a medical paper found in her mother’s belongings, and J.T. (Austin Basis) worries that Cat’s visits to the warehouse loft leave Vincent vulnerable to discovery by Muirfield’s agents. Catherine encourages Vincent to help her investigate deeper into the Muirfield project, but when Vincent refuses, Cat investigates on her own, until her computer is wiped clean by a malicious virus. Tess tries her hand at dating again, but soon discovers that she’s unknowingly involved with a married man. Heather (Nicole Gale Anderson) moves out of Cat’s apartment after growing uncomfortable with her sister’s quest for more answers about their mother’s death.
– Iris (Lara Jean Chorostecki), a Bosnian immigrant, is arrested on the suspicion of killing a judge for deporting her brother. Vincent (Jay Ryan) insists that Iris is innocent, so trusting his instincts, Cat (Kristin Kreuk) works behind-the-scenes to uncover the truth. When Cat’s actions disrupt the investigation, Joe (Brian White) places her on leave. Nevertheless, she continues on her own to discover that Iris is hiding a family secret, and needs Vincent’s help. JT (Austin Basis) is concerned that Vincent risks exposure to Murifield by helping Cat, leading Cat to work out a way to communicate with Vincent without seeking him out.
Vincent (Jay Ryan) revives a 19-year old boy who was left for dead in a dumpster and rushes him to the E.R., where he remains in a coma. After Evan (Max Brown) declares that the boy's x-rays reveal a history of bone fractures, Cat (Kristin Kreuk) and Tess (Nina Lisandrello) question the father, Zachary Holt (guest-star Alex Carter), who worries that his son's ADHD and history of fighting and gambling might have gotten him mixed up with the wrong crowd. The detectives question Lois Whitworth (guest-star Madchen Amick), who owns the Westchester Polo Club where the boy worked. Lois is surprised to learn that her daughter, Clarissa (guest-star Jenn Proske), has been dating this young man. Clarissa claims that she ended the relationship because he was involved in illegal activities, but Cat and Tess suspect that there's more to her story. Meanwhile, Silverfox (guest-star Peter Outerbridge) and his Murifield agents track down Cat, and offer to tell her the truth about her mother in exchange for turning over Vincent, who they insist is a monster. Cat tells Vincent about her Silverfox encounter, and Vincent realizes that Cat might be afraid of him. JT (Austin Basis) wants them to flee, but Vincent refuses to leave Cat, instead offering to surrender to Silverfox in exchange for Cat's safety.
Vincent (Jay Ryan) is captured on a convenience store surveillance video while preventing a robbery, and Cat (Kristin Kreuk) warns him to be extra careful when his photo appears in the newspaper. Cat and Tess (Nina Lisandrello) investigate the disappearance of a woman named Amy (guest star Annie Murphy), who has gone missing after her fiance, Dr. Michael Walters (guest star Jeremy Glazer), surprised his bride-to-be by placing their engagement announcement in the paper that morning. Evan (Max Brown) runs Amy's fingerprints and discovers her true identity, while Cat wonders if her disappearance was intentional after Vincent mentions that he and JT (Austin Basis) have an escape plan to clear out of their loft without a trace in a matter of minutes. Later, Michael also goes missing and Joe (Brian White) learns that his team has been deceived. Meanwhile, Heather (Nicole Gale Anderson) is planning a surprise birthday party for her sister, forcing Cat to postpone her birthday plans with Vincent. At the party, Cat and Evan share a surprising moment.
After she’s seemingly stood up by Vincent, Catherine wonders if it’s because he saw her kissing Evan at her birthday, but Vincent mysteriously blacked out on his way to meet Catherine and is now searching for answers. Catherine’s case pulls her into the sophisticated world of the SoHo art scene. When Vincent finds Catherine all dressed up to go to a gallery opening -- with Evan -- he has to admit that his feelings for her are growing deeper.
JT (Austin Basis) thinks Vincent (Jay Ryan) may somehow be involved in Cat's (Kristin Kreuk) homicide investigation after she mentions a local college fraternity brother was brutally killed. JT examines Vincent to determine the cause of his increasingly frequent blackouts, but when Vincent starts to beast out, JT is forced to tranquilize him. Meanwhile, Evan and his new intern find a strange cut on the victim's ankle, which matches that of a female cadaver left on campus a year earlier. As Evan works to uncover more clues from the crime scene, he is kidnapped. Cat begs Vincent to help find Evan and save his life, yet she doesn't realize that she's putting Vincent's life in serious danger.
JT (Austin Basis) suspects that Catherine (Kristin Kreuk) is the trigger of Vincent’s (Jay Ryan) blackouts, so to disprove this theory, Vincent allows JT to inject him with endorphins and sedatives that force him into a fugue state. In flashback, Vincent recalls his time in Afghanistan when he received his first super soldier shot, and remembers who injected him with the DNA altering substance. He also recollects how the other soldiers experienced unpredictable side effects, including fugue states, and is relieved to know that Cat isn’t causing his blackouts. Vincent shares his memory about Murifield with Cat, who experiences some recollections of her own. Then, as Cat and Tess (Nina Lisandrello) investigate the attempted murder of a teen pop star (guest-star Max Schneider), Evan suspects that Cat is deliberately protecting the vigilante who saved him in the subway.
When Catherine's (Kristin Kreuk) dad (guest-star Rob Stewart) gets remarried, the bride-to-be and her bridesmaids try to find the daughter-of-the-groom a date for the wedding. Uncomfortable with being set up, Cat reluctantly admits that she's seeing somebody and confides to Vincent (Jay Ryan) that she wishes he could be her date. At the wedding reception, Cat learns about a research grant that Evan (Max Brown) received to study the mutant DNA cells found at local crime scenes. When she tells Vincent about Evan's theory of how the cells are changing to become more animal-like and less human, she encounters an unexpected detour that could change the course of their relationship. Meanwhile, Tess (Nina Lisandrello) and Joe (Brian White) cross the line romantically despite the fact that Joe is a married man.
Vincent (Jay Ryan) barely escapes being caught by his former fiancée, Alex (guest star Bridget Regan) and must deal with the repercussions of his past. While Cat (Kristin Kreuk) is in the hospital, she is forced to confront her feelings for Vincent. Meanwhile, J.T. (Austin Basis) gets a surprising visitor asking about old research he did on mutant DNA.
Vincent (Jay Ryan) is torn between his new feelings for Cat (Kristin Kreuk) and his old memories with Alex (guest star Bridget Regan). J.T. (Austin Basis) learns that Evan (Max Brown) is planning to propose a task force to catch the beast and must figure out how to stop him. Meanwhile, Tess (Nina Lisandrello) investigates the mysterious skydiving death of the wife of a billionaire adventurer, while Cat remains off duty until she recovers from being shot.
Cat (Kristin Kreuk) suspects Muirfield might know Vincent’s (Jay Ryan) whereabouts and in spite of her vow to go cold turkey, she is forced to interrupt his romantic cabin getaway with Alex (guest star Bridget Regan) in order to save their lives. Meanwhile, Evan (Max Brown) finds a bug in his lab and becomes increasingly suspicious of J.T. (Austin Basis).
Cat (Kristin Kreuk) and Vincent (Jay Ryan) are unsure if they can trust Alex (guest star Bridget Regan) with the truth about his past. Evan (Max Brown) realizes that Claire (Kelly Overton), the woman he is dating, is hiding things from him. Heather (Nicole Gale Anderson) meets and falls for Joe’s (Brian White) younger brother Darius (guest star Christian Keyes), and Vincent tries to win over Cat with romantic gestures for Valentine’s Day.
After a dinner where Cat (Kristin Kreuk) introduces Vincent (Jay Ryan) to Heather (Nicole Gale Anderson) ends badly, Heather enlists Tess (Nina Lisandrello) to stage an intervention with Cat. Evan (Max Brown) receives an interesting proposition that could change the course of his cross species investigation and at an event to honor Joe (Brian White), Heather goes missing and Vincent is forced to make a tough decision that saves her life.
New Assistant District Attorney Gabe Lowan (Sendhil Ramamurthy) arrives at the precinct, suspicious that cases involving the vigilante are being mishandled, and wanting answers. Cat (Kristin Kreuk) is determined to protect Vincent (Jay Ryan) at any cost, which includes tracking down a witness and threatening him at a gala masquerade ball. Meanwhile, Vincent worries he may lose control if he gets romantically involved with Cat.
After taking their relationship to a new level, Cat (Kristin Kreuk) and Vincent (Jay Ryan) are forced to deal with reality when someone appears to be the framing the vigilante. Evan (Max Brown) finds proof that Cat knows more than she is letting on about the beast. Muirfield and the police are closing in on Vincent and this time there is no escape, so J.T. (Austin Basis) and Cat come up with an extreme solution. Meanwhile, Tess (Nina Lisandrello) following a tip, finds something that will forever change her relationship with Cat.
Cat (Kristin Kreuk) is forced to reveal things that she had been keeping from Tess (Nina Lisandrello) to salvage their relationship, and to protect Vincent (Jay Ryan). Gabe (Sendhil Ramamurthy) is suspicious of everyone in the department, while Evan (Max Brown) witnesses Cat doing something that changes his opinion of her, making him even more determined to track down the beast.
Evan (Max Brown) confesses his love to Cat (Kristin Kreuk) and admits that he tipped off Muirfield to Vincent's (Jay Ryan) whereabouts. Meanwhile, Gabe (Sendhil Ramamurthy) finds evidence that someone in the department is a mole who was working with the vigilante.
Gabe (Sendhil Ramamurthy) comes clean to Cat (Kristin Kreuk) that he knows about Muirfield. Vincent (Jay Ryan) does not think Cat should trust Gabe and is suspicious of his intentions, which causes tension between them. Meanwhile, JT (Austin Basis) and Vincent finally find a new place to live.
On the anniversary of her mother’s death, Cat (Kristin Kreuk) asks Gabe (Sendhil Ramamurthy) to attend her family’s annual remembrance of Vanessa, which makes Vincent (Jay Ryan) incredibly jealous. Cat learns some information that makes her think her mom might still be alive and when a sniper shoots the mayor at a public event, Vincent finds evidence that links Gabe to the sniper.
(Kristin Kreuk) and Vincent (Jay Ryan) go on a date out in public in an attempt to be a normal couple, which backfires on them. Meanwhile, Gabe (Sendhil Ramamurthy) reveals some information that gives Cat hope they can find a cure for Vincent.
When secrets about Cat’s (Kristin Kreuk) family are revealed, it will change everything Cat knew about her past. Vincent (Jay Ryan) finds himself staring his demise in the face; while Gabe (Sendhil Ramamurthy) takes drastic measures get some answers.