A poignant, funny, and tender story of sibling rivalry – and devotion. When his little sister unexpectedly shows up at his door after 16 years, a mixed martial artist decides to take her in and eventually train her to become the next big fighter. However, when her skills progress and she develops her own ideas of the sport and its darker underside, it upsets their longstanding dynamic outside of the ring. As they fight with and for each other, the siblings grapple with hidden selves, loss and finding the strength it takes to let go in a knockout bout to become each other’s ultimate champion.