In Theatron, a civilization divided by a fortified trench called the Cut, immortal beings known as Players reside in a massive, sentient theatre called the Playhouse. The Players wield Craft, a power that lets them manipulate thoughts, suspend reality, and shapeshift. North of the Cut, citizens bear Eleutheraen marks, golden symbols burned into skin that shield against Craft and bind the bearer to truth. South, unmarked Revelers worship the Players. The Playhouse's director, Silenus Darstellar, controls the Players through a book of divine power called the Script.
The story opens 10 years before the main events. Eight-year-old Riven Hesper and her older brother, Galen, wait at a courthouse to receive their marks when a Player breaks free and freezes everyone except Riven. The Player tries to lure her away through Compulsion, a form of Craft that overrides will, but Riven resists by stabbing the Player's hand with her father's Eleutheraen gold knife. The Player's golden blood sinks into her skin before guards subdue the creature.
Ten years later, Riven is 18 and slowly dying from what she believes is a curse from that blood. Her skin has turned gray, her bones ache, and her body refuses to heal. The Playhouse returns to the District of Dionysus, shared territory between North and South, and Silenus announces a Great Dionysia: a five-day festival during which a mortal fights the Lead Player for a place in the cast. Galen, now a council adviser, has secretly revoked Riven's academy acceptance, crushing her hopes. Their father, Michail Hesper, a renowned Peacemaker who brokered the treaty confining Players to the South, was found dead on the Playhouse steps 15 years earlier.
Desperate, Riven enters the Playhouse hoping to steal the Script. She encounters Lead Player Jude Stepharros, who is charismatic rather than monstrous. When Jude discovers she is marked, he proposes a bargain: He believes someone wants him dead, so he has chosen Riven as his contender under a false name, intending to reveal her marked status to forfeit. In exchange, he promises to cure her.
During training, a sabotaged chandelier crashes toward the stage and a shard pierces Riven's lungs. Unable to use Craft because of her mark, she demands Jude destroy it. He burns through the symbol, forcing her to sign the Playhouse contract first. Craft floods in, saving her life but severing her oath to truth. Through the Playhouse's mirrors, which serve as portals, Riven learns the Players plan to cross the Cut and that the North's Eleutheraen gold is depleted, leaving its defenses a bluff. She devises a plan to capture Jude and trade him to the council for a new treaty.
Riven completes a Craft binding with Jude that links their life forces. Her body heals, with gold flecks appearing in her irises. Backstage, she glimpses Gene Hunt, the former Lead Player who supposedly died years ago. Gene appears damaged, her skin peeling to reveal gold, and fires an arrow at Riven before vanishing. The Playhouse breaches the Cut by force. During a training session, Gene materializes and attacks Jude, who transfers his life to Riven to survive. Riven plunges into his memories of a childhood in Thymele, a city destroyed by Northern armies. She debates letting him die but releases him, then takes his appearance onstage through Mimicry, a form of Craft-based shapeshifting.
Riven forces Jude out of the Playhouse at arrowpoint. On a train to the Northern city of Syrene, she notices the scar on his palm and realizes he was the Player who confronted her as a child. Jude escapes. Riven is captured by bounty hunters, but Jude returns in disguise, kills their leader, and rescues her. Their journey back transforms their relationship: Both admit they care for each other. Jude reveals a golden gash spreading across his chest, similar to Gene's deterioration, and confesses he is dying.
At the Playhouse, Galen, who infiltrated the theatre searching for Riven, slips her a vial of pure Eleutheraen gold. Before she can react, Eleni, a former bounty hunter now in a council guard uniform, drives her father's Eleutheraen knife through Galen's back, killing him. Overwhelmed by grief, Riven uses Compulsion to kill Eleni, despite Eleni being marked and theoretically immune, then unleashes a wave of darkness across the city. At a public trial, Riven reveals her identity as the Peacemaker's daughter, uses Craft to sway the crowd, and challenges Jude to the Great Dionysia. Silenus declares the festival will begin the next day.
The festival opens with three days of performance. On the fourth night, Riven whispers each castmate's true name, breaking their fourth walls, the illusions binding them to their scripted identities, and restoring their real memories. All agree to return to a well on Mount Eleutherae and release their Craft back into the world. Jude alone refuses.
Silenus reveals the truth: Riven is not human but one of the original Players, ancient beings who emerged from the well on Mount Eleutherae. Silenus drained its power, bound the Players to his Script, and caged them in the Playhouse. Every Player's identity is a temporary "costume" worn over an eternal being. Michail was not Riven's father but a mortal who agreed to raise a disguised Player as his child so that, when the treaty expired, "Riven" would return as the first marked Player, opening the North permanently. Michail tried to flee after learning the truth; Jude killed him. Gene, who also discovered the truth, tried to warn audiences before Silenus poisoned her. Players who become too aware of their nature deteriorate physically, their costumes peeling away, as is now happening to both Jude and Riven.
Riven forces the council to sign Silenus's terms by revealing the North's depleted gold, a betrayal she views as necessary to prevent outright destruction. On the final night, she dips her last arrow in Galen's vial of Eleutheraen gold. In the arena, Jude tries to provoke Riven into killing him as scripted, but she refuses. She fires the arrow into the dome, cracking the Playhouse, and uses Compulsion to order the audience to evacuate. The Players move the crumbling theatre to Mount Eleutherae and begin ascending toward the well.
Jude follows Riven outside but races back in, insisting one of them must hold off Silenus. Riven follows. Inside, Jude grabs Silenus by the throat to provoke Nyxene, the Playhouse's shadow guardian bound to protect its director. As Nyxene tears into him, Jude channels his remaining Craft into a shield. He shouts "Script!" and Riven understands. She pours the Eleutheraen gold over the Script. The book and the Playhouse erupt in golden flames.
The Playhouse explodes. Figures descend into the well, and Craft floods back across Theatron. Marks vanish, and the world gradually forgets the Players. An epilogue set years later reveals the Players persist as spirits haunting theatres. Riven and her fellow Players, Mattia, Titus, Arius, and Parrish, attend a play based on their story. Afterward, a man holds a door for Riven. She notices a ring on his finger and a freckle below his left eye. He grins: "Between you and me, I've never cared for Tragedies." Riven recognizes Jude, reborn but unmistakably himself.