A brief folk verse traces the ways mortals have tried to protect themselves from the Players. A treaty confined the Players to the South. A wall was built when the treaty ended, and mortals received marks in case the wall failed. It ends with a plea for divine mercy if the marks fail too.

Ten years later, 18-year-old Riven navigates fearful streets. Citizens smash their mirrors as news confirms that the Playhouse is returning to the District of Dionysus at the 500-year treaty’s end. She crosses the Cut—a trench sealed with protective Eleutheraen gold dividing the North from the Player-worshipping South. In the shared District, she visits her only friend, Haris. Haris is a “Reveler” (an unmarked Playhouse fanatic) who believes that Riven’s condition is a blessing. When she offers him a protective pendant, he grabs her wrist in rage, bruising her fragile skin. She leaves as he brandishes his hand mirror, repeating his belief that the Playhouse is returning. As mirrors serve as portals for Players to travel through, Haris hopes to be transported to the Playhouse.

Riven stops at a bookstore to collect school materials. The marked owner informs her that healers predict she has less than a month to live. Riven has been accepted into the Orkestrian Academy to study healing. She intends to find a cure for the curse destroying her body since no outside healer can undo the actions of a Player. Other patrons call her ugly and remark on her corpse-like appearance. Since marked people can’t lie, Riven knows they’re telling the truth. As she leaves, the Player’s whispered threat that she would suffer echoes in her mind.

Riven sees the Playhouse erupt from the earth at the center of the District. Worshippers flood toward it while marked citizens scatter. Through the open Playhouse doors, Director Silenus Darstellar’s voice announces a Great Dionysia and a casting call—an opportunity for Revelers to become Players.

Later, Riven’s aunt Cassia shows her a solagraph of an executed Player named Iris. For years, Riven has sought the identity of the Player who cursed her, but Iris isn’t the woman from the courthouse. Cassia advises Riven to stay home and avoid mirrors.

At home, Riven finds Galen visiting and a letter revoking her academy acceptance. Galen, who is now a council advisor, admits that he petitioned the academy’s board due to her physical fragility. He also reports that after the Playhouse arrived, Lead Player Jude Stepharros killed a guard and blocked treaty negotiations until after the casting call. Their argument grows fierce, and Riven invokes their father’s murder, a forbidden subject. Galen warns that her temper will destroy her and then leaves. Riven follows him out.

Riven wanders the empty District at night and is drawn toward the Playhouse by music—a phenomenon associated with Players and the deadly historical Dancing Plague. Three masked Revelers ambush Riven, intending to sacrifice her, before a voice from inside the Playhouse compels all three to cut their own throats. Director Silenus emerges, mistakes Riven for a late auditionee, and consults the Script—a glowing book that she believes might reverse her curse. Badly injured and desperate, she enters the Playhouse.

Riven slips backstage in search of the Script and hides in a corridor where several Players emerge: Titus, a powerfully built Tragedian; Mattia, the oldest Player on record; Arius, a Comedian whose singing Craft once marched an entire army off a cliff; and Parrish, who hoards macabre trophies. As Silenus introduces each through the ballroom curtain, they file out. When he announces Lead Player Jude, a voice behind Riven asks why she’s hiding. She turns to find Jude himself.

Jude mistakes Riven for a nervous auditionee and attempts to calm her. When she admits that she’s not there to audition, he speculates that she came to steal, noting her gaunt appearance. As the crowd chants his name, Jude rises to make his entrance, pressing a gold ring with an inscribed motto, “Finders Keepers,” into her hand and suggesting that she sell it for food. Riven pockets the ring, resolving to find Silenus’s dressing room and steal the Script.

Lost in the Playhouse, Riven finds a common room leading to three dressing-room corridors. A large mirror shows her own reflection for the first time in years: sunken and corpse-like. She hides when Jude enters, but he finds her immediately. He attempts to use Craft to compel her to drop a fire poker, but her mark deflects it. She attacks, pressing her Eleutheraen blade to Jude’s throat. He tries Craft again and reaches for her hand. The skin contact causes both to recoil with nausea, and he realizes that she’s marked. Hearing Silenus approach, Jude drags Riven down the Mimicry corridor.

Jude pulls Riven into the late Gene Hunt’s old dressing room. Gene is a former Lead Player who famously died on stage while urging the audience to run. When pressed for her name, Riven gives the alias Alistaire Hunt. Silenus enters, and Jude announces Riven as his chosen contender for the Great Dionysia.

In a flashback to 10 years earlier, Riven sits in class studying solagraphs of the five Players, puzzled that none match her attacker from the courthouse. The professor explains the origins of the 500-year peace treaty. Silenus agreed to it in exchange for the release of a captured Player. Riven faints.

Alone with Riven, Jude explains his plan. He must fight the last mortal standing, and he will ensure that Riven outlasts the other contenders in the Great Dionysia. Then, he will expose her marked status, disqualifying her and ending the contest. The scheme will protect him from the competition, as he anticipates a threat against his life from within the Playhouse.

Jude is scornful when Riven offers him compliments on his appearance, clarifying that the Three Compliments rule is “a myth.” When Riven attacks Jude, he easily restrains her, and a violent coughing fit leaves her helpless. She admits that a Player poisoned her and that she came for the Script. Jude offers to cure her in exchange for cooperation. He takes her knife and shoves her through a mirror portal.

Riven emerges in the Playhouse arena with four other contenders before a vast Reveler audience. Silenus warns the auditionees that this is their last chance to leave before signing a binding contract. He states three rules: Never wish an actor good luck, avoid the dark, and never break the fourth wall. The survivor faces Jude in the final match, and killing Jude earns the winner a cast role while elevating their mentor to Lead Player. Riven realizes that Jude has never competed in a Great Dionysia and engineered this arrangement to avoid ever having to.

Jude takes Riven to a rooftop cast party. Silenus reports that a spy sent by Dorian, a legendary Player Bounty Hunter, infiltrated the casting call. He sends Parrish to deal with the intruder. Parrish returns with a box of the spy’s bloody teeth as trophies for her collection. Riven publicly goads Jude and dumps a wine basin on his shoes in hopes of getting expelled. Titus screams when an Eleutheraen-tipped arrow, shot from outside, strikes his ankle. Jude identifies it as the weapon of one of Dorian’s agents. He orders an early departure and conjures a concealing fog. Riven’s escape attempt fails as the Playhouse begins to move.

The Playhouse relocates to the coastal city of Koilon. Locked in her dressing room, Riven fashions an escape rope from curtains and sheets. Jude intercepts her on the balcony and explains that the Playhouse is an illusion that he can shift to any location. He uses a medical kit to treat her injuries from the Revelers’ assault. When he insists that she must have her mark burned off to survive the competition, Riven refuses. A shadow resembling a clawed hand—belonging to Nyxene the Stage Manager—appears briefly in a darkened corner. Jude warns that Nyxene is lethal and protects Silenus. When he tells Riven that she can’t leave while he lives, she resolves to kill him.

Riven contacts Haris through the portal of his hand mirror. He’s euphoric to learn that she’s in the Playhouse. She bribes him with the promise of Jude’s ring in exchange for an unspecified favor, and he agrees.

Riven meets the four other contenders: twins Thyone and Phileas, Tig, and Linos. All four underwent a Craft binding with their mentors overnight—a transfer of borrowed power that turned their eyes gold. However, Riven forfeited hers by refusing Jude. In the dining hall, the Players debate invading the North before its armies can mobilize. Silenus arrives and announces costume fittings followed by an assessment in stage combat and Reality Suspension.

In the costume wing, Riven resists removing her jacket to hide her mark. Jude arrives and, using Mimicry to disguise himself as a silver-haired designer, takes her measurements. He urges her to slash her mark before the assessment and hands her a prop metal blade. When Riven tells Jude she hates him, an unexplained twinge in her throat puzzles her. Jude insists that she doesn’t mean it.

On the stage, Titus and Parrish demonstrate stage combat and Reality Suspension. They show how a performer’s life force temporarily transfers into a partner’s body when they die, making an onstage death reversible with sustained eye contact and shared Craft. Titus corners Parrish, holds her gaze, speaks a word, and then kills her. Jude warns Riven that her mark seals her life force inside her body, meaning any death on this stage will be permanent.

Titus carries Parrish’s corpse offstage. Mattia then swings at Jude as a demonstration. He deflects and wounds her arm, presenting it as a lesson in never underestimating your opponent. Jude tells Riven that he can only make her death quick. Enraged and determined not to be quietly killed, she impulsively volunteers to fight.

Riven grabs a dagger and faces Mattia. Midway through the fight, Jude spots a ghostly white figure racing along the catwalk and sprints backstage. Mattia knocks Riven down; Riven recovers and slashes Mattia’s torso and then is cornered and disarmed. Jude shouts a command from the catwalk, reality briefly bleaches of color, the figure vanishes, and a chandelier drops toward the stage.

In a flashback to 10 years prior, Riven wakes in the nurse’s office after fainting in class. A young healer with a bandaged hand dismisses the nurse’s concern that Craft entered Riven’s blood. Riven feels unwell and another, unfamiliar sensation. When Galen asks what’s wrong, she’s compelled to admit that she’s angry.

Riven regains consciousness in her dressing room with a shoulder wound and a collapsing lung from the chandelier’s impact. Jude, tending to her, explains that he suspended reality in an effort to save her, but her mark undermined the efficacy of his Cast. Desperate to live, Riven tells him to remove the mark. Jude makes her sign the Playhouse contract first, and she signs as Alistaire Hunt. He retrieves a heated iron, warns her that betraying his Cast will mean death at his hands, and instructs her to hold his gaze. As the iron burns off her mark and her breathing fails, he speaks a word, and her life force finally breaks free, transferring into him.