Tree Gelbman is the main character in the horror film series "Happy Death Day." She is a college student who finds herself trapped in a time loop, reliving the day of her murder repeatedly. Each time she dies, she wakes up on the same morning, giving her the chance to uncover her killer's identity. Throughout the films, Tree evolves from a self-centered individual to a more compassionate person. As she navigates the challenges of the time loop, she learns valuable lessons about friendship, love, and personal growth, ultimately striving to break the cycle and save herself.