To uncover the conspiracy of an organization, a colleague infiltrated the prison where the mastermind was incarcerated, only to suffer a mental breakdown. To save a friend and expose the darkness, Shou disguises himself as a male prison officer and infiltrates a women-only prison. Amidst the uncertainty of who the informant is among the prisoners, officers, and colleagues, he was supposed to keep his female identity hidden... A fierce struggle begins within the unyielding cage where no one comes to help.