Merlin is entrusted by Berched to look after the Young Tarlach. Merlin is unhappy with the situation, but he quickly changes his mind after hearing that Starlet is also helping.
Merlin and the Milletian go out to look for Culinary Artist because of Young Tarlach's disapproval of Starlet's cooking. Merlin and the Milletian capture a Juiciest Boar, attracting the Culinary Artist. Afterwards, the group enjoys themselves to a feast.
Culinary Artist requests the group to deliver some ingredients to Glenis before flying off. The group then takes a walk to Dunbarton by cutting through Abb Neagh, however it begins to rain, forcing the group to take shelter at the nearby Bard Camp. During the night, an Enslaved Neid attacks the group, but the Milletian and Merlin are able to defeat it.
As they arrive at Dunbarton, Tarlach gets separated from the group only to wind up right next to Kristell. Tarlach, unwilling to follow the group, wishes to stay with Kristell as the group decides to complete her errands. She then sends the Aces to deliver donations to Emain Macha's cathedral.
With everything finished in Emain Macha, Merlin and the Milletian head back to Dunbarton to pick up Young Tarlach. Kristell advises them to take a rest in Port Cobh after they arrive. Along the way, Tarlach mentions having nightmares but refuses to explain what they are about.
The next morning, Tarlach is suddenly missing. Annick mentions that she knows a certain someone heading to Bangor that may be able to locate him. Once the two meet them, Merlin tries to request Treasure Hunter's services, but he walks away upon hearing that there is trouble at the Dragon Ruins.
Merlin and the Milletian try to convince Treasure Hunter to help them, but an Enslaved Crumena attacks. After defeating the Enslaved Crumena, Treasure Hunter is intrigued with Merlin's ability and agrees to help. Treasure Hunter searches Port Cobh, mentioning that the dock workers saw a boy. He also finds traces of his hair there, further deducing that Tarlach went to Iria.
The trio arrive at Port Qilla, they meet Pinky, Treasure Hunter's gorilla pet. Their investigating concludes that Tarlach went through the Mana Tunnel. Treasure Hunter suspects he went to either Kaypi Canyon or Maiz Prairie. Treasure Hunter leaves to investigate Maiz Prairie on his own, handing Merlin a magical map that will pinpoint his location to Treasure Hunter.
Regrouping with Treasure Hunter at the Dragon Bone Tomb, Treasure Hunter accidentally drops The Black Book of Bith into the water, summoning Aliens. After recovering the book from the creatures, Merlin detects nearby footprints; Treasure Hunter notes they are headed to Neres Plateau and the tracks are fresh.
At Neres Plateau, they meet Lopez who claims to have seen the boy, but refuses to talk until Treasure Hunter pays him. He claims Tarlach was accompanied by black-robed people and they went to the Connous Oasis. Treasure Hunter doesn't believe him as the tracks lead to Rupes Desert, but Merlin goes to the oasis to investigate, taking the Milletian with him. At the oasis, Lopez ambushes them with Bandit Cutpurses and Treasure Hunter eventually jumps into the fight. After defeating the bandits, Merlin interrogates one of them and learns that they were going to rob Filia's medical supplies.
After heading to Filia, the group meets with Atrata, who tells them that the bandits attacked only recently and could not have gotten far. Treasure Hunter then leads the group to Errans Gorge where they see an injured Lopez. Treasure Hunter interrogates him to reveal that Tarlach went to Cor.
Continuing with their mission, they talk to Tupai, who reveals he had seen Tarlach along with "dark spirits" yet refuses to talk until they go to The Holy Land of Shamans.
At the holy land, the group oversees the unconscious Millia, who mysteriously reacts to Treasure Hunter's Black Book of Bith. She temporarily regains consciousness to recite a dark omen, surprising Merlin. Akule inspects the dangerous item but cannot make a word of it, advising Treasure Hunter to not open the book in the holy land and find someone to seal it up. Akule then tells Merlin and Treasure Hunter to watch over the Milletian before they set out. As they leave, Treasure Hunter mentions that Tupai told him that the black-robed people talked about a Hot-Air Balloon and Hot Springs, indicating that they are at Zardine.
The group saves a Dying Glutton Monkey at the Hot Springs with medicine, which then tells Pinky about the whereabouts of the kidnappers.
Treasure Hunter deploys a hot-air balloon. As they board the balloon, they see the black-robed people's balloon nearby take off. Treasure Hunter's balloon follows suit and the Milletian uses the Ballista to take down the attacking Enslaved Wyverns and Enslaved Alpha Wyverns. The group eventually catches up to the Kidnapper's Hot-Air Balloon and shoots it down near Calida Lake.
When they approach the downed balloon, the kidnappers, revealed to be Cessair, summon Enslaved Ifrit to distract them as the Cessair leaves with the boy. After defeating the creature, Treasure Hunter summons a pair of Shires and the group follows the Cessair.
The group follows the Cessair to Barba, now pursuing them on skis. During the chase, Treasure Hunter manages to successfully recapture Young Tarlach and the group flees to La Terra Highlands.
They set up a camp as the group notes that the Cessair put Tarlach to sleep via magic. Treasure Hunter then takes watch duty as Merlin sleeps, but wakes him up when the Cessair appear and orders Merlin to make an escape raft. They manage to hold the Cessairs off, but quickly plan to escape.
The group is then forced to raft with the Cessair in pursuit. Upon reaching Cor, a trap activates and the raft explodes, knocking everyone unconscious and allowing the Cessair to freely take Tarlach and Pinky.
Following the Cessair to Metus on a horse chase, Merlin rushes forward and attempts to snag Tarlach. He snags Pinky, failing to see through her disguise. Heading into Metus, the group are ambushed by enemies. Once the enemies are cleared out, they find that the Cessair and Tarlach have vanished. Treasure Hunter notes that the altar is actually a portal and opens it.
Upon opening the portal, they use it and end up at Muyu Desert. Treasure Hunter then instructs Merlin to read the Book of Bith, to which the latter manages to make out numbers in the ancient language. Suddenly, a pyramid-like structure appears before them as if reacted by the book and they investigate. They find themselves at Nemeton afterwards.
Spotting numerous Cessair, the group ambushes a patrol to steal their robes in an attempt to blend in. They then find themselves at the Cessair training grounds and are forced to play along to not get caught. However, after it is revealed in a eventual round that the Cessair are forced to fight each other, Merlin fears that he may be pitted against his allies. He openly drops his disguise, forcing Treasure Hunter and the Milletian to break off from the stealth plan. They then promptly defeat the Cessair Instructors before fleeing.
Heading up the tower, Merlin tries to persuade the guards into letting them pass, but they refuse to permit them entry and order them to show their faces. They immediately recognize the intruders, using their Red Eye magic to knock the Milletian unconscious before being dispatched. Treasure Hunter uses something given to him by Akule on the Milletian. While Treasure Hunter tries to get the door open, Merlin falls asleep, causing him to continue without Merlin.
Afterwards, Merlin is attacked by groups of Cessair and Cessair's Heart. He manages to fend them off, only to be lured into a trap and is prisoned with the Milletian, who had just regained consciousness. Ruairi approaches the two and notices Merlin, saying he is after the God Fragment in Tarlach. Ruairi explains they intend to remove the God Fragment from Tarlach for their plan. Before he leaves, Ruairi gives them a crystal and says Tarlach wanted them to have it. Merlin takes the crystal and turns it into a wand that allows him and the Milletian to teleport out of the barrier.
Pressing forward, they encounter Pinky without Treasure Hunter, who left them a note saying he plans to stop Dian, the mastermind of the Cessair and Tarlach's kidnapping. As Merlin tries to break open the door ahead, he suddenly hallucinates but returns to reality, courtesy of the Milletian.
Pushing further, they encounter Dian and an unconscious Treasure Hunter. The two manage to defeat her, however the ritual surrounding Tarlach still continues. The group pushes further, with Merlin saying Treasure Hunter now owes him.
The Milletian, Merlin, and Treasure Hunter push forward to stop the ritual surrounding Young Tarlach, but are constantly delayed by Ruairi, Cessair's Heart, Adniel, Cessair, and a barrier. Treasure Hunter disables the barrier and Merlin does his best to hold off the enemies. However, when the barrier attempts to restore itself, Merlin summons every ounce of his strength to push back the Cessair, teleport the Milletian onto the altar with Ruairi and Tarlach, and teleport himself and Treasure Hunter outside Nemeton before it explodes due to the altar.
After the Milletian and Ruairi fight in their final battle, Ruairi destroys the altar and sends the two plummeting down to Erinn. Merlin, on Treasure Hunter's hot-air balloon, stops the Milletian's descent by putting them in a magic bubble. Ruairi is then engulfed in a bright light.
Although the ritual was not stopped and Ruairi successfully opened the door to another world, Tarlach is teleported next to the group. Merlin demands to talk to the God Fragment, scaring Tarlach, before being kicked by Treasure Hunter. They note that Tarlach is now a regular boy. Merlin orders the Milletian to take Tarlach back home. As the two walk off, Treasure Hunter asks Merlin why he attacked Tarlach about the God Fragment. The latter mentions a secret group that protects Erinn. Merlin then asks Treasure Hunter for his real name.