Hello Monster (also known as I Remember You) follows Lee Hyun, a brilliant criminal profiler with a dark childhood, who returns to South Korea after a mysterious incident from his past resurfaces. Teaming up with the passionate and tenacious elite detective Cha Ji-an—who has secretly been observing Hyun for years to solve her own family's tragedy—the duo forms a specialized crime-solving unit. As they delve into a series of intricately connected murders, they realize that a dangerous psychopath from their shared past is orchestrating the games, leading to a complex web of psychological warfare, hidden identities, and questions about whether monsters are born or made. The series brilliantly balances procedural crime-solving with deep, character-driven psychological drama. At its core is the complex emotional bond and tension between Hyun and his estranged, deeply troubled younger brother, Lee Min, who grew up walking a very different, darker path. As the boundaries between justice, vengeance, family, and morality blur, the characters must confront their deepest traumas and decide how to face the monsters lurking both in society and within themselves.