Seo Hoon is an unknown idol in his third year since debut. When illegal footage of his younger brother, Eloy—who was a successful idol in contrast to him—is leaked, he assaults another idol during a live broadcast for insulting his brother. Afterward, Eloy takes his own life, and Seo Hoon’s life also plunges into ruin. <Heartbeat Island> is an extreme deserted island survival reality show that gathers celebrities like Seo Hoon whose lives have fallen into despair after causing controversy. “The culprit who ruined Eloy’s life is there.” Drawn in by a phone call from a mysterious figure, Seo Hoon participates in the 10-day reality show to uncover the truth behind his brother’s death.