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.

While attempting to figure out what had happened, the remaining guests discover that their radio is not working, effectively leaving them stranded on the island with the culprit until the typhoon passes. They also quickly discover that Kinzo has gone missing as well. Battler and the rest of the family come up with the theory that one of the eighteen people on the island is posing as Beatrice in an attempt to claim Kinzo's inheritance. The three primary suspects are the servants, who have access to the entire mansion; Natsuhi, who was the last person seen with Kinzo; and Eva, who has the most to gain from the murders. However, after a heated argument between Natsuhi and Eva, they are unable to come to a definitive answer and return to their rooms. Later, Eva and Hideyoshi are found to have been murdered in their locked room.

Everybody tries to determine how Eva and Hideyoshi could have been killed when an odd smell begins to fill the mansion. Kanon goes to investigate the boiler room along with Kumasawa, but is mortally wounded in the process. The rest of the family and staff arrive and discover the dying Kanon, as well as Kinzo's partially incinerated body. They decide to retreat to Kinzo's study, which should be the safest room in the house. After they enter, however, a letter from Beatrice mysteriously appears. Since Genji, Nanjo, Kumasawa, or Maria are the only possible suspects for planting the letter, Natsuhi forces them to leave the study. Later that night, the phone rings with Maria singing on the other end. Natsuhi, Battler, George, and Jessica rush downstairs to find Genji, Nanjo, and Kumasawa murdered and Maria standing in the corner, still singing.

Upon being pressed about the murders, Maria tells them that Beatrice is the culprit, though Battler refuses to accept this explanation. As they argue, Natsuhi bars everyone inside the room and demands Beatrice show herself. By the time everyone breaks out of the room, they see Natsuhi as she drops dead, apparently having commited suicide. Golden butterflies soon fill the room, and the remaining survivors are killed. Afterward, everyone is brought to Purgatory, revived and joking about how they should have solved the epitaph rather than determine who was committing the murders. However, everyone except Battler is convinced that the culprit is a witch. When Battler insists that everything that happened could have been carried out by human means, he is confronted by Beatrice herself, who challenges Battler to prove that the murders were not caused by magic. Beatrice discusses the events she has set into motion with a rival, Bernkastel, who plans to lend her own powers to assist Battler.

After one of the family meetings in 1984, Shannon admits to Jessica that she has a crush on George. Eva mentions that George will be taking part in an arranged marriage to keep Shannon away. Shannon prays for help from Beatrice, who appears and makes a deal with her: in return for smashing a mirror in the island's shrine that limits her power, Beatrice will guarantee George's love. Shannon at first refuses, but in 1985, succumbs to temptation and smashes the mirror. In 1986, Jessica confides to Shannon that she has a crush on Kanon. Jessica manages to convince Kanon to come to her school festival, where Kanon is perplexed at seeing a different side of Jessica. He refuses to get into any relationship with Jessica, stating that people and furniture are never meant to be together. He then confronts Beatrice and accuses her of toying with people's emotions. Beatrice merely laughs and says that no matter what happens, her power will return and the path to the Golden Land will be opened.

Battler and Beatrice begin their debate of logic vs. magic from Purgatory when the Ushiromiya family members gather for their annual conference. This time, however, Beatrice appears in the real world as an important yet anonymous guest. During that day, Maria is left outside by her mother Rosa as punishment for constantly talking about Beatrice. When Rosa returns to save Maria from the coming storm, Beatrice appears before them and hands envelopes to both of them. Meanwhile, Shannon discovers Beatrice's devious intentions and decides to resist her. Later, when George proposes to her and asks her to give him her answer by the next day, she accepts immediately. During dinner, the siblings discover their guest to be Beatrice and eventually come to acknowledge her as a witch.

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.

Everyone finds Jessica's body in her locked room, while Kanon's is nowhere to be found, having been erased by Beatrice. After the notion of Kanon killing Jessica is deterred since he gave Jessica his master key, the other servants are marked as the most likely suspects. Battler, meanwhile, finds himself unable to think of any way the crime could have been carried out while knowing the servants are innocent. Rosa sends the servants off, hoping to use them as bait to draw out the culprit. In the process, the servants stumble across Kanon, severely wounded but apparently still alive, who tells them that Rosa was the one who attacked him. However, it is soon discovered that this Kanon is a duplicate created by Beatrice. The fake Kanon attacks the servants, killing Nanjo and Kumasawa before being destroyed by the other servants.

The servants try to explain what happened to the others, but when they return to the room where Nanjo and Kumasawa were killed, their bodies are missing. In an effort to gain Rosa's trust, the servants give their master keys to her. Still suspicious, however, Rosa sends the servants off once again, this time with George deciding to accompany them. Put off by Rosa's paranoia and not wanting to suspect his family and friends, Battler begins to accept Beatrice as a witch. Meanwhile, the other servants learn about the mirror Shannon smashed, and remember that Natsuhi was in possession of a similar mirror, which they believe should help them. George, Shannon, and Gohda retrieve Natsuhi's room key from her corpse, but are chased by Beatrice and her furniture along the way. The three manage to enter Natsuhi's room, but Gohda is killed by Beelzebub while he tries to keep the witch's furniture at bay, allowing Beatrice to confront George and Shannon herself.