Adu Du recaps the previous episode where he contacted Bago Go and fainted due to the steep prices of his merchandise, then being enraged at Probe for selling his spaceship for an electric spatula until he learns that Probe also got a free Mukalakus robot (power source excluded) with the deal. He thinks it to be the perfect weapon to defeat BoBoiBoy, and powers it up with their leftovers of Tok Aba's cocoa.
BoBoiBoy and his friends sit at a playground, lamenting about him having to leave Rintis Island. Ochobot is saddened to learn that he can't go with him since Tok Aba needs help at the shop. As BoBoiBoy reassures that things will be fine, a sudden explosion causes them to painfully fly off the jungle gym. From the clearing dust appears the giant Mukalakus robot, with Adu Du piloting on the inside. He quickly overpowers Ying and Yaya, then eventually Gopal, despite BoBoiBoy's attempts to stop him. Adu Du tries his laser on BoBoiBoy as well, but he runs out of power, giving the hero enough time to do an Triple Split and fight back.
Adu Du isn't defeated just yet, and gives Probe the cue to capture Ochobot and throw him into Mukalakus as its new power source. Thunderstorm and Cyclone can only contend with Mukalakus for so long until he overpowers them both and has them in his grasp. An exhausted but determined BoBoiBoy Earth pleads Adu Du to stop, even as the latter keeps firing lasers. His pleas turn into a loud command, and Adu Du sees Earth about to unlock his new power, and drops the other two elementals to attack. Before he can stop him, Earth transforms into Quake, gaining new rock gauntlets and control over a golem the size of Mukalakus, resistant to its laser attacks. He throws some punches at the robot before Thunderstorm and Cyclone return to his side and they fight together, defeating Mukalakus and Adu Du. BoBoiBoy merges back and faints next to Ochobot.
note BoBoiBoy awakes at home, bandaged like the rest of his friends there are, who have been waiting for him to wake up, and thank him for saving them. BoBoiBoy asks what happened to Adu Du and Probe, but Tok Aba tells Ochobot not to reply, stating that he needs the rest. Three days later, Tok Aba and BoBoiBoy's friends show up at the train station to send BoBoiBoy off. They exchange sentiments, making it for a proper send-off, and BoBoiBoy assures them that he'll return someday and will never forget them. They wave goodbye as the train leaves while BoBoiBoy gives them a thumbs-up out of the window.
Meanwhile, Adu Du announces up at a greying sky that despite BoBoiBoy having won this time, Adu Du would return. Probe then requests he return to their new make-shift shelter base as it would rain soon. 6 months later, the Rintis Island kids are back in school, and the class teacher of BoBoiBoy's friends announces that a new student would be joining them. BoBoiBoy then appears in the doorway, and his friends are overjoyed.
This episode provides examples of:
- Giant Mecha: Mukalakus, a large destroyer robot which Adu Du pilots from the inside and fights Team BoBoiBoy with.
- Sequel Hook: 6 months after BoBoiBoy heads home, his friends are back at school and hear of a new student joining their class. The credits music begins to swell as BoBoiBoy appears in the doorway, and his friends are overjoyed.
- Slow-Motion Pass-By: As BoBoiBoy boards the train to send him home, another boy, one with spectacles and poofy raven hair, walks out of the train through the same doorway. As they walk past each other, the backdrop turns blue with a white flare center as time appears to slow down, before the backdrop fades and they walk at normal speed again. note
