Masquerade of the Guilty

Leaving Sumeru behind, the Traveler and Paimon arrive at Romaritime Harbor, where they meet the magician siblings Lyney and Lynette and first hear of the prophecy hanging over Fontaine: one day its people will dissolve into the waters of the sea, leaving only the Hydro Archon weeping on her throne. In the Court of Fontaine, the theatrical Archon Furina stages a public welcome for the newcomers and invites them to Lyney's magic show at the Opera Epiclese.

The show ends in catastrophe: the trick goes wrong and the body of a missing girl is discovered, entangling Lyney in the case of Fontaine's serial disappearances of young women. Put on trial before the Chief Justice Neuvillette and the infallible Oratrice Mecanique d'Analyse Cardinale, Lyney is defended by the Traveler — and mid-trial reveals that he, Lynette, and Freminet are Fatui agents of the House of the Hearth, serving the Harbinger Arlecchino.

The Oratrice acquits Lyney, but suspicion falls on another Fatui Harbinger: Childe. Protesting his innocence, he demands a trial by combat, loses the duel against the champion Clorinde, and is sentenced to the Fortress of Meropide. The true culprit remains at large, and the Traveler resolves to stay and dig deeper — wary of Furina's showmanship and the prophecy no one can explain.

Determined to solve the disappearance case from another angle, the Traveler joins forces with Navia, president of the Spina di Rosula. At the Fountain of Lucine, the Traveler makes contact with an Oceanid who was once one of the missing girls — proof that the victims were dissolved into water. An ambush by unmarked Clockwork Meka nearly kills them before Clorinde intervenes, an uneasy rescue: years ago, Clorinde slew Navia's father Callas in a formal duel.

The trail leads to Marcel, respected head of the Confrérie of Cabriere — in truth Vacher, the serial killer who abducted young women and dissolved them with water from the Primordial Sea, seeking a cure for his long-lost companion who had melted away at his side. In the old case, he framed Callas, who chose a duel to the death to shield the Spina di Rosula from ruin. Exposed at trial by Navia and the Traveler, Vacher is convicted by the Oratrice.

Navia finally learns the truth of her father's sacrifice and begins to reconcile with Clorinde, while the voices of the dissolved find a measure of peace. Neuvillette, moved in a way no human should understand, lets a quiet rain fall over Fontaine — light rain, falling without reason. The Primordial Sea, and the prophecy tied to it, now loom larger than ever.

The Harbinger Arlecchino demands custody of the imprisoned Childe — only for Neuvillette to discover that Childe has vanished from the Fortress of Meropide without a trace. Since the courts hold no jurisdiction over the underwater prison, Neuvillette asks the Traveler to investigate from within: under the deliberately absurd charge of eating a cake meant for Furina, the Traveler and Paimon are sentenced to forty-five days behind bars.

Inside, the enigmatic administrator Wriothesley, Duke of Meropide, personally shows them around, and they meet the Melusine head nurse Sigewinne. Lyney, Lynette, and Freminet have smuggled themselves in as well, on orders from "Father": Arlecchino has confirmed that Furina does not possess the Hydro Gnosis, and wants the fortress's forbidden depths investigated. Navigating the prison's coupon economy and its whispered "hidden rules," the Traveler slowly earns the inmates' trust.

Strange visions of Childe's imprisonment guide the Traveler onward. Loyal prisoners finally admit the "hidden rules" were a cover story: Childe, hearing a mysterious voice, escaped weeks ago through the maintenance pipes. But the passage he took is now completely flooded, and the act closes with a new plan — Freminet, the diver, must follow Childe's trail into the drowned depths below the fortress.

The covert investigation unravels when Lynette disappears from the infirmary and a furious Lyney confronts Wriothesley — who, it turns out, has known about the Fatui infiltration all along. The standoff breaks when Clorinde carries in an unconscious Freminet: while retracing Childe's escape route he was poisoned by Primordial Seawater, whose concentration beneath the prison is rising dangerously. Enemies become allies, and the fortress's secret is laid bare — at its bottom lies a sealed breach into the Primordial Sea itself.

The seal fails. As the deadly water bursts through, Neuvillette arrives, forces the sea back with a power no judge should wield, and closes the sluice again. Above, at a tea party in the opera house, Arlecchino drops her pleasantries: she once came for Furina's Gnosis in the night, found none, sensed only a strange "curse" — and is now certain that the trembling Archon of Fontaine is no god at all.

The Traveler pieces the final clue together: Neuvillette is the reborn Hydro Dragon, the ancient Sovereign whose authority the usurping Heavenly Principles carved up to create the Archons. Only with the Hydro Archon's authority returned could he avert the prophecy. Far below, Childe drifts awake in the Primordial Sea — a colossal narwhal circling above him.

The prophecy begins: Primordial Seawater erupts beneath Poisson, dissolving its lower town — among the dead are Navia's faithful retainers Melus and Silver. With Furina still evading every question, Neuvillette, Navia, the House of the Hearth siblings, and Clorinde conspire with the Traveler to force the truth out the Fontainian way: an elaborate trap delivers Furina onto the opera stage for her own trial. Prosecuted by the Traveler, she is proven a fraud — she is no god at all. Yet the Oratrice sentences the "Hydro Archon" to death, and the sea-devouring narwhal from Childe's dream tears into the opera house.

A single tear reveals everything to Neuvillette: five hundred years ago, the Archon Focalors split herself in two — a divine will hidden inside the Oratrice, and the human Furina, condemned to play the goddess alone, forbidden to tell a soul, all to deceive Celestia. In the Erinnyes, Focalors has Neuvillette execute her upon the guillotine, shattering the Hydro throne and returning his full Sovereign authority — which he spends to grant every Fontainian a truly human body as the great flood breaks.

Wielding Neuvillette's borrowed power, the Traveler destroys the All-Devouring Narwhal; the mysterious Skirk returns Childe from the Primordial Sea. Fontaine survives its apocalypse. Neuvillette rules on as sovereign Iudex, publicly absolving Furina, who steps down into an ordinary human life — her five-hundred-year performance honored in silence.

A commission leads the Traveler and Paimon back to Sumeru's Vimara Village, where everyone remembers a kind young man who went missing — yet no one knows his name. The girl Atossa recalls hours spent talking with him at dusk, during which the sun never seemed to move. Dainsleif joins the investigation into the Abyss Order's renewed activity and finally names the "Sinner": Vedrfolnir the Visionary, his own elder brother and one of the Five Sinners of Khaenri'ah.

The missing villager turns out to be Caribert, the cursed child who exists only in implanted memories — the foundation of the Abyss Order's Loom of Fate. Now fully unlocked, the Loom can weave Ley Lines and rewrite the world itself; the idyll of Vimara Village was Caribert's own creation, a stolen chance at the life he was denied. Having lured Dainsleif into a trap so the Traveler's sibling could face him alone, Caribert says his farewells and fades away in peace.

Within the collapsing memory, the Traveler at last stands before their sibling — unable to touch them, and destined to forget the encounter. The sibling confides their race against the Heavenly Principles, which did not stir even when the Hydro throne was destroyed, and their loneliness on the path they chose. Waking with no memory of it, the Traveler finds a parting gift in their pocket: a picture of themselves, their sibling, and Caribert.