After dinner is over, Maria reads a letter she says she received from Beatrice earlier. The contents stipulate that Beatrice will take everything the Ushiromiya family owns if no one can solve the witch's cryptic epitaph. While Kinzo's sons and daughters try to ask him what this is about, they are not able to enter his study. The rest of the night has the adults staying up still discussing the family inheritance while the children retreat to the guesthouse. That night, George gives Shannon an engagement ring, and asks her to give her reply the next day. The following morning, six people have gone missing, and Natsuhi is informed of a strange symbol drawn on the outdoor tool shed. When she goes to investigate with Kanon and Genji, they find the missing six people brutally murdered inside. After Genji goes to fetch Dr. Nanjo to inspect the bodies, Battler, Jessica and George follow and see the horrific scene themselves. Among the dead are Krauss, Rudolf, Kyrie, Rosa, Gohda, and Shannon.

Rosa's siblings and their spouses go missing, while the remaining guests find the chapel door locked. Finding the key inside the envelope Beatrice gave Maria, everyone enters and find the missing people murdered inside, along with some of Kinzo's hidden gold. Jessica and Kanon are ambushed by Beatrice, who summons her legion of goat servants against them. Kanon fights off the goats until Beatrice summons two Stakes of Purgatory, Asmodeus and Satan, who kill Jessica and Kanon. In Purgatory, Battler and Beatrice suspend their game to determine how the first six people could have been murdered inside a locked room. Battler begins forming several theories, but Beatrice counters most of them, using red text to speak the truth. However, Battler manages to catch Beatrice off guard by theorizing that the culprit could have taken the key from the envelope, locked the dead bodies in the room, and put the key back where it was. Beatrice congratulates Battler, but remains confident he will submit.

Beatrice and her predecessor engage in a magic battle, though a surprise attack allows Beatrice to kill her teacher. Battler is bewildered by the entire spectacle, but regains his composure when the former Beatrice, under the new name Virgilia, reappears and gives him advice for countering Beatrice's claims, allowing him to deny that the witches' battle ever took place. In the real world, the siblings discover the bodies of Kinzo and the servants, each locked in a room containing the key to the next locked room, forming one large locked room. With Virgilia's guidance, Battler theorizes that one of the six victims is the murderer, created five of the locked rooms, and then died in an accident in the sixth room, forcing Beatrice to concede this round. Meanwhile, Eva, urged on by the vision of her younger self, solves the riddle of Beatrice's epitaph and discovers Kinzo's hidden gold.

In 1998, Ange interrogates relatives of the Rokkenjima murder victims and hires a boat captain to take her to Rokkenjima, discovering Sakutaro's torn remains as well. In 1986, the cousins are informed of Kinzo's test from the hostages in Kuwadorian and are forced to lock Gohda and Kumasawa in the storehouse to keep them from interfering. Jessica and George are individually tested by Ronove and Gaap, respectively, and instructed to choose which of the islanders will be next to die: themselves, their true loves (Shannon for George and Kanon for Jessica), or everyone else. Jessica chooses herself for Kanon's sake so that he may live his life to the fullest, while George chooses everyone else as he is willing to go so far for his love for Shannon to be accepted. Unwilling to leave the hostages in the dungeon, however, Jessica and George defiantly engage their respective demons in combat.

Ange enters the Golden Land where she happily reunites Maria with Sakutaro and forces Beatrice to continue the game. Battler, however, has lost his soul due to his uncertainty of his own identity. Desperate to revive Battler, Ange confirms his qualifications as Kinzo's grandson, and reveals her own identity as his sister to him, successfully restoring him. Having broken the most important rule as a piece in the game to keep her identity a secret, however, Ange dies. With Battler's resolve strengthened and Beatrice realizing she cannot escape the game, the two engage each other in their final confrontation, with Battler's blue truth against Beatrice's red truth. Kinzo's spirit appears to protect Beatrice, but Battler dispels him in blue by confirming his death not only at the start of the fourth game, but every game thus far; however, Beatrice confirms in red that there are actually no more than seventeen people on Rokkenjima. Nevertheless, Battler manages to explain all four games through human means, while Beatrice is left completely skewered by his blue truth, but unable to die. Beatrice begs Battler to kill her and presents him the last mystery she is able to give: since Battler is the only person left alive on the island, and yet Beatrice is also there to kill him, Beatrice asks, "Who am I?" Understanding Beatrice's plight, Battler promises to solve her final mystery and put an end to her suffering. Bernkanstel and Lambdadelta, however, intend to keep Beatrice in the game, torturing her for eternity.