|“||You know she's in there. And you know she's stronger than you are.||”|
— Seth to Amaru about Kate
Seth and Kate first met in the fourth episode of season one Let's Get Rambling. Beginning as antagonists, all the events that unfold around them bring them closer and they end up caring a lot about each other. To Seth, Kate and Richie are the people he cares about the most in the world. To Kate, Seth, Scott, and Richie are the only people left alive that she cares about.
Seth and Kate are currently partnered up with Richie and robbing banks together.
When they arrive at the Titty Twister, Seth punches the bouncer after he made comments about Kate being part of the menu. Inside the local, Seth confesses he has killed good people because they stood between him and his freedom in front of Kate, her father, and her brother, after stating that they all are a family, messed up, but still a family, and he playfully asks Kate if she forgives him. He pressures her into saying "Yes, I forgive you".
After the attack following Santánico's show, Sex Machine appears and Kate recognizes him as the man who had tried to hit on her earlier, and Seth immediately points his gun at him calling him a "sick son of a bitch".
While they are trying to find a way out of the Twister, Seth is constantly trying to protect Kate, usually shielding her with his own body.
They got separated when Seth went in search of his brother who had been shot earlier.
They reunite outside the Twister after Richie has left Seth to go with Santanico and Kate has mercy-killed her father to prevent him from becoming a Culebra.
Kate asks Seth if he needs company and after a few seconds, Seth says yes. They get on the Corvette and drive off into the sunset.
Season 2 starts about 3 months after the events of season 1. During this time Seth and Kate have moved constantly along the border, living off of Seth's scores, usually planned by Kate, who chooses their targets.
Seth has resorted to the use of drugs as a way of coping for the loss of his brother. Kate seems unimpressed with his coping methods, but helps him nonetheless, assisting in injecting him with heroine.
Seth and Kate got closer and grew to care about each other since after all that has happened, they are the only people who understand each other and whom they can trust.
While planning a shot at the Mercado of the city they're living in, Seth snaps at Kate since she can't blow the lock, and he thinks they won't be ready for the hit. She answers that she now understands why Richie has left him and that he's impossible to work with. She goes on saying that even if she has lost both her brother and her dad inside the Twister, she is strong to not resort to drugs as a way of coping. She tells him that she had to kill her father because he had been poisoned with culebra venom, and he didn't want to turn into a monster, so when he asked her to kill him, she drove a stake into his heart. Hearing this, Seth stops and looks at her, then goes to sit in front of her and says that she had never told him that. Kate successfully blows the lock and hands it to Seth. In the car going over their plan, Seth says to Kate "ready partner", with Kate responding with a wide smile.
During the shooting that follows their shot inside the Mercado and the arrival of The Regulator, Seth always protects Kate.
Afterwards, they have a huge fight inside the car as they get away from the shooting's place because Kate states that she's not ready for what they are doing and that she still wants to find her brother. Seth again tells her that her brother is gone and that everybody that she has ever loved is dead. At this point, Kate yells at him to stop the car, and when he does she steps out after being given from him the passport he has had made for her.
While he's driving away, he realizes he can't leave her like that and goes back, leaving the car and most of their money to her.
They remain separated until the end of the season, and when Seth is told by Richie that Kate was killed by Carlos, he's visibly stricken, and while Richie talks about how to bring Carlos down, he seems completely lost and confused, like he can't believe Kate is really dead. He angrily tells Richie that all he's done is using her and getting her killed. Richie answers that he used her too during their months together to organize their scores. Seth angrily attacks Richie.
During the rest of the episode he constantly mentions Kate, and when he comes face to face with Carlos, her killer, who tells him that Kate is dead because of Richie, he warns him not to use her name.
After Carlos is dismembered, Seth beats up Richie saying that every time they fly solo it all goes to hell, like when their uncle Eddie was killed, and this time, Kate was killed.
As he stands in his office alone and sadly sighs, the scene moves to Kate's body near the Blood Well. The Santa Sangre comes out of the pump and gets into Kate's wounds, possessing her and this way, bringing her back to life.
Seth currently believes Kate is dead and has no idea that she has, on the contrary, been resurrected. Her current mental state is unknown, as well as which side she stands on.
Six months after Kate's death, Seth while fighting in the fight club, he had caught a glimpse of Kate, unaware that her body has been possessed by Amaru, Queen of Xibalba. Later, Richie had confirmed that Kate is alive, but she is possessed by an entity. They had confronted Ximena Vasconcelos and Burt about the situation with Kate and Amaru and the real reason why Amaru had possessed Kate's body and had her demon helpers killed the Lords. Seth wanted to get Amaru out of Kate's body, but Burt told him they can't and that Kate's gone. Later, he learns from Burt the real reason why Amaru is on this realm, to open the door to Xibalba to unleash hell on earth.
At this point, Seth is determined to get rid of Amaru and is convinced that Kate is truly gone, despite the fact that Scott and Richie both believe Kate is still fighting inside her body to break through. This is proved right when Seth confronts Amaru and she provokes him by repeating the same words he said to Kate the first time they met ("What was it that you said to her? "Stick with me and you'll make it through without any bumps or scrapes, right?") and Seth is visibly touched by her words. In the meantime, Scott is able to injure Amaru, allowing Kate to break through. She begs Seth to kill her as she can't keep fighting against Amaru. Seth can't believe that it's actually Kate speaking, but then he does and tries to reach out to touch her but Amaru regains control and almost kills Seth, before Scott stops her. She is in a way able to look into Seth's soul.
From this point on, Seth wears gloves to protect himself from another eventual contact with Amaru, probably being aware that knowing Kate is still inside her, he wouldn't be able to trust himself to be focused around her.
When Seth and the group decide to perform and exorcism on Amaru to expel her from Kate's body, Amaru once again uses Kate against him and constantly provokes him. He tells him he's nothing without his brother, that he's a coward and that he will never kill her because by doing so he would also kill his precious little Kate. She also tell him that the hate he feels around them is all Kate, who blames him for everything that happened to her. When Amaru leaves temporarily Kate's body, Seth immediately releases her from her ties. She desperately asks him why he did that to her and he tearfully confesses he didn't want to hurt her but just to break Amaru. He tells Kate to keep fighting because he knows she's stronger than Amaru but Kate tells him the Queen of Hell let them capture her only to play them and to get what she really wanted. Seth continues to stroke Kate's face and tries to maintain her focus on him. Amaru tries to regain control once again and Seth tells Kate he's sorry for what he did to her but she answers that she doesn't forgive in before giving in to Amaru once again. Seth is visibly stricken by her words.
After learning that Amaru plans to regain control over her original body, Seth wants to stop the ritual in order to free Kate of her. However, he tells Santanico and Burt that if they can't manage to do that, they will have to finish Kate, because at this point it's clear that he could never be able to do it.
After managing to kill Brasa and the other Xibalbans sent by Amaru, Seth sees in the distance the church in which Amaru is holding the ritual to get her body back. He realizes Kate will die if he doesn't get there in time and starts to run towards it. In the meantime, Kate's body has been freed, but is badly hurt and she's seen lying on the ground bleeding out.
In the last episode of Season 3, Seth gives his blood to Kate in order to save her life. When she regains consciousness, he wants to send her away to protect her, but accepts the fact that she needs to be there to stop Amaru. During the episode he constantly tries to protect her and worries about her. Initially, when she tells him she has to go through the gate to Xibalba to defeat Amaru (dying in the process), he refuses to allow her to do it. Kate with glassy eyes then tells Seth "time to let go partner". Seth with a devastated expressions looks at Kate and understands that it is the only way to stop the Queen of Hell, he lets her go.
In the end, both Kate and Richie make their way back from Xibalba and together they are able to stop Amaru. Seth and Richie are seen leaving the spot together while Kate smiles at Seth.
After an indefinite amount of time, Seth and Richie are shown inside a car preparing for a hit. They pronounce their usual quote with Seth saying "Here's to getting rich and fat" and Richie saying "And dying in the arms of a beautiful woman". At this point, Seth disagrees, saying that part of the quote doesn't work anymore. This is explained when they attack the bank and Kate joins them, as she is now partnered with them.
- Both of their fathers are deceased.
- Both of their brothers are culebras.
- Both of their mothers are no longer in their lives: Seth's mother left him and Richie, when he was young and Kate's mother is deceased.
- Seth is very protective of Kate right from the moment they first meet.
- To Seth saving Kate is like saving a part of himself.
- They spent the 3 months together after the Titty Twister.
- Seth became emotional after hearing about Kate's death.
- After Kate's resurrection, Seth is the first one to see her.
- Seth continuously believes Kate is alive despite constantly being told she’s not by everyone including Richie.
- Seth fought for them to save Kate.
- Seth and Kate would do anything to save each other.
- Seth tells Kate he's sorry for what he did to her, but she says she doesn't forgive him, later learned that she does in fact forgive him as he, along with her brother, are the people she loves.
- Seth has to ask Burt and Santanico to finish off Kate if things go bad as he is unable to hurt her in any way.
- Seth and Kate share the same blood type (This is discovered when Seth gives his blood to Kate to save her life).
- Kate clearly states that Seth, along with her brother Scott, is one of the people she loves.
- Kate, now a partner to Seth and Richie, pronounces Seth's usual line "Be Cool".
- As of now, Kate, Seth and Richie are together.