Diane throws Gilthunder out of the forest and decides to accompany Meliodas, Elizabeth and Hawk on their travels. Their next stop is Baste Dungeon, where Ban, the bearer of the Fox's Sin of Greed, has been imprisoned for five years. However, Meliodas collapses suddenly from his injury and they decide to stop at Dalmary Town, letting a doctor named Dana treat him with medicine. There, Diane and Elizabeth both show care for Meliodas, but display envy towards each other due to their opposites in strength and size, with Diane ultimately deciding to leave to find Ban herself. Unbeknownst to them, Dalmary Town is currently under the rule of the Weird Fangs, a unit in the Holy Knights, who are determined to kill Meliodas and Diane, and capture Elizabeth. Dana also unexpectedly reveals to a shocked Elizabeth that the supposed medicine he administered is a deadly poison, while Golgius, a member of Weird Fangs, appears out of the blue to escort her back to the Kingdom of Liones.

Golgius attempts to take Meliodas' sword, only for him to awaken with no sign of being poisoned, proceeding to intimidate Golgius with an aura that prompts him to flee, but not before stabbing Dana for failing his task, revealing how he kidnapped his daughter Sennett in exchange for his cooperation. Using his power of invisibility, he attempts to kill Meliodas but is defeated and forced to retreat by force. The three head out to Baste Dungeon, but encounter Diane, who suddenly attacks them after succumbing to hypnosis by Ruin, another member of Weird Fangs pretending to be a shepherd, at the sound of his bell. Meliodas is soon hypnotised as well and the two begin to fight each other, mistaking the other for a Holy Knight. Meanwhile, Ban, having escaped prison, strips the apprentice Holy Knight Jericho of her armour to disguise himself and slip out, but is subsequently stabbed in the chest by his captor Jude.

As Meliodas and Diane continue to fight each other under hypnosis, the fourth and final member of Weird Fangs, Friesia, attacks the disguised Ruin with her insects, prompting Elizabeth to risk her life to protect him. However, as Ruin reveals his true identity, he realises that Elizabeth was going for the bell on his staff the whole time, successfully freeing Meliodas and Diane from the spell to defeat Ruin and Friesia respectively. Meliodas, Hawk, Diane and Elizabeth, who is being carried in Diane's bag, infiltrate Baste Dungeon to rescue Sennett, and find Ban wandering around the prison as well with no sign of having been injured, causing the dungeon's collapse during their happy reunion and breaking a secret barrier that Golgius set up in the process. The six of them regroup back at Dalmary Town, where Dana, who survived the attack, treats them to a meal as courtesy. Meanwhile, King, the bearer of the Grizzly's Sin of Sloth, is shown to be allied with Gilthunder and the rest of the Holy Knights.