S1·E14 Positional play

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.