|“|| "What do you want, Allison?"|
"To not be scared. That night at the school, I felt utterly weak. Like-like I needed someone to come in and rescue me. I hate that feeling. I want to feel stronger than that. I want to feel powerful."
"Allison, if you can just give me a little bit of time... be just a little patient... I think I can give you exactly what you want."
— Kate and Allison in Wolf's Bane
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Kate, as Chris Argent's younger sister, was Allison's aunt, and as a result, they had been close since Allison was very young; according to Allison, she saw Kate more as a sister than she did as an aunt. However, due to the Argent Family's legacy of being Hunters of the supernatural, a fact that was kept secret from Allison until she was over seventeen years of age, both Allison and Kate constantly moved around, which prevented the two from seeing each other for several years. They reunited shortly after Allison, Chris, and Victoria Argent moved to Beacon Hills, California, as Kate came to visit to help Chris and Victoria hunt the Alpha who was terrorizing the town.
Unfortunately for Kate, Allison began to grow suspicious of how secretive Kate and her parents were being about what they did for a living, especially when Kate and Chris had conflicting stories about the reasoning behind Kate's car trouble, causing her to suspect that her family was keeping secrets from her. In time, it was revealed that Kate was actually behaving this way on purpose because she disagreed with Chris and Victoria's decision to shield Allison from the supernatural world, and to get around this stance, Kate began leaving clues for Allison to figure out their Hunter legacy for herself, first by giving her the Argent wolf pendant, and then by leaving a flash-bang arrowhead where Allison could find it. After Allison's life was threatened by the Alpha at the high school, Kate began teaching Allison how to defend herself using tasers and her mini-crossbow.
Finally, after Kate and her Hunter cohorts managed to capture Derek Hale, who was wrongly accused of the murders committed by the Alpha, she revealed the Argent family secret to Allison-- they hunt werewolves and other shapeshifters and supernatural beings who pose a threat to humanity. After Allison learned that her then-boyfriend Scott McCall was a werewolf and had hidden this fact from her and that her best friend Lydia Martin had been attacked by the Alpha, she was so upset that Kate easily manipulated her into helping her hunt the werewolves down. However, it wasn't until Allison and Kate had incapacitated Derek and Scott that Allison realized Kate intended to kill them, a request she refused to fulfill.
Before Kate could kill Scott herself, the Alpha (who had recently been revealed to be Peter Hale, a survivor of the Hale House Fire set by Kate six years earlier) arrived and dragged her into the house's remains. He forced Kate to apologize for decimating the Hale Family by threatening Allison's life, but after deeming her apology insincere, he ripped Kate's throat out with his claws as Allison watched in horror. Allison believed her to be dead, but unbeknownst to anyone, Kate had actually survived as a result of how deeply Peter's claws dug into her skin, transforming her into a Werejaguar. Unfortunately, Allison and Kate never had the chance to reunite before Allison was killed by an Oni demon during a battle. Upon learning of Allison's death, Kate sought revenge on Scott McCall, as she blamed him for her death and the decimation of her own family. The two remain separated, as Allison is still dead and Kate is on the run from the Calavera Family and her brother, Chris.
Throughout Teen Wolf
In Smoke and Mirrors, at the end of the battle of Kate, Peter, and Kate's Berserker versus the Calavera Hunters and the McCall Pack and their allies, Chris Argent finally managed to track an injured Kate to the temple under La Iglesia after shooting her with a yellow wolfsbane bullet. Afterward, Kate accused Chris of wanting to kill her, which Chris denied, though he claimed he didn't want to save her anymore, either. Kate used this as an opportunity to call him out for making her the bad guy and argued that Scott McCall and his friends weren't Chris' heroes before accusing them of killing Allison. This made Chris furious as he reminded her that Allison died saving her friends and pointed out that Kate wouldn't die for anyone before Kate fled the scene.
- According to Allison in Magic Bullet, she and Kate had a relationship more akin to sisters than that of an aunt and a niece, though it had been a few years since they had last seen each other.
- Peter Hale remarked on the resemblance between Allison and Kate, though he did remark that Allison seemed less "damaged" than Kate was.
- Both Allison and Kate were manipulated and corrupted by Gerard Argent's influence, though Allison's dark arc was only temporary, whereas Kate's has become more or less part of her personality.
- After Allison's resurrection, she began having hallucinations of Kate rising from the dead and having fangs and claws, which was ultimately proven to be somewhat accurate in the episode after Allison's death, when it was revealed that Peter's claws had turned Kate into a Werejaguar, which allowed her to self-resurrect right before the full moon in Season 2's Shape Shifted. It is possible that these hallucinations were psychic in nature, perhaps as a side-effect of the surrogate sacrifice ritual that required Allison be sacrificed and resurrected.
- Kate sought to avenge Allison's death by turning Scott McCall into a Berserker in hopes that his pack would kill him, as she blamed him for killing Allison, though, as Chris Argent reminded her, Allison died saving her friends from the Oni and was not killed by them as she insisted.