When Bunga and Simba are trapped underground, they discover a shared family background – they were both raised by Timon and Pumbaa.
Simba and Nala call for their children, Kion and Kiara, as they begin to make their way to the first elephant concert of the season, hosted by Ma Tembo and her herd in Mizimu Grove. As they race along, Ono swoops down from the sky to alert Kion to a group of antelope that have gotten themselves stuck in the mud. Reluctantly, Kion decides that his role as leader of the Lion Guard takes precedence over his social life, and he leaves to sort out the problem. Simba assures Kion that the elephants will understand and Nala says that taking care of the Pridelands is his duty as leader of the Lion Guard. The family continues their journey, with Kiara telling her father that she'd be okay with attending concerts as part of her duties. As she runs ahead, Simba starts to notice the ground shaking. He and Nala call for her to get uphill, but it turns out there warning of a sinkhole is too late. Simba rushes over, flinging Kiara over to Nala, who grabs her in turn. Just as she attempts to run, the sinkhole emerges. Whilst she and Kiara make it safely to the high ground with Simba pushing them up, Simba himself finds himself unable to hold on, and tumbles into the sinkhole, causing his mate and daughter great worry. Not too far away, Kion and the Lion Guard are assisting the antelopes that were stuck in the mud, when the tremendous rumble of the sinkhole alerts them to a new problem. Ono flies ahead, seeing the new sinkhole as well as Nala and Kiara beside it. Kion asks if his father is okay, but Ono reports that he can't actually see from there. Fuli insists that Kion go ahead whilst they clean up, and Ono leads the way over. Back at the sinkhole, Simba emerges from a clump of rocks. He confirms that he's okay, although he is unable to climb out, as there is nothing to climb onto. Ono then leads Kion to the sinkhole, where he asks his mother if his father is okay. She confirms that he is and that he is indeed stuck. Suddenly, Bunga, Beshte, and Fuli appear having completed their mission. Without thinking, Bunga leaps over the sinkhole and plummets down, landing softly on Simba's mane. Simba is unimpressed to see Bunga (as well as having his mane tangled by the honey badger's fall), and despite Bunga's enthusiasm, points out that he cannot, in fact, rescue him from down there. Kion calls down asking if they're okay, to which Simba replies positively. Ono swoops down to see if there is any way for them to climb up but becomes startled when rocks fall onto his head. He flies back up and reports. As Beshte walks closer to the edge, it begins to break away further. Nala calls for everyone to move away, but Kiara is caught, almost falling through. Fuli acts fast and rushes in, saving her from falling in with her father and Bunga. Everyone starts to organize a plan on how they can rescue Simba and Bunga. Meanwhile, Bunga makes a few suggestions on how to escape the sinkhole. He eventually decides to draw back, running as fast as he can and leaping back up the walls. This, in turn, causes more of the walls to collapse, and he and Simba become buried in more rocks. As everyone at the top start to worry, Ono swoops down to check on them. Lion and honey badger turn out to be fine, though Simba chides Bunga for acting without thinking. Kion then gets an idea on how to save them. He runs off with the Guard to put his plan in motion. Simba tells Nala to go on ahead to the concert with Kiara, knowing that Kion will save him soon. Nala is hesitant but agrees nonetheless. Just as she and Kiara leave, the Guard return with a giant log, tipping it into the sinkhole. Unfortunately for them, it hits the bottom and breaks into hundreds of tiny splinters. Bunga then snacks on some bugs that have fallen and notices a tunnel in the side of the sinkhole. Simba knows that it could possibly be the Nandembo Caverns, thus providing a way out. He calls to Kion, letting him know of this. Kion calls back that he will meet him at the entrance to the caverns, hopefully meeting up there instead. Kion and his friends leave the sinkhole area, as do Simba and Bunga as they enter the tunnels together. As Simba and Bunga traverse through the dark tunnel, Simba soon starts to become frustrated at Bunga's random route choices, since no consideration is being taken on which ones he chooses. Simba's annoyance with the honey badger soon causes an argument to erupt between the pair, with Simba roaring to get his point across. This ultimately causes a cave in, and their disputation escalates so much that they wander off in different directions. Simba is relieved to be away from Bunga and soon starts to realize that he is, in fact, going the right way. This also leads him to the conclusion that Bunga must be going the wrong way. He soon remembers that no matter how annoying he is, Bunga is still his subject, and starts to backtrack for the little honey badger. Meanwhile, Bunga slowly starts to cool down, hoping that Simba would return for him. When he mistakes some rocks for being Simba, he states 'no worries', which reminds him of his uncle's favorite song, which he begins to sing. As he is singing Hakuna Matata, Simba starts to hear his echoes and sings along with him. The two soon find each other in a clearing, and Bunga is surprised that he knows it. Simba explains that he was raised by Timon and Pumbaa before he was and that they used to sing it to him all the time when he was growing up. Bunga then realizes that it sort of meant that they were like brothers, to which Simba agrees with. As the two laugh softly, Simba laments about how Timon and Pumbaa could not be there to see them finally getting along. Meanwhile, Kion and the Guard have entered the tunnels, even managing to get Timon and Pumbaa involved. The pair cry over their lost cubs, though Bunga and Simba soon hear their echoing cries. They race across the caverns, following the voices until they find the source. A large ravine separates them, however. Simba, with Bunga on his back, copies Bunga's earlier idea, by running and leaping across whilst the pair yell Zuka Zama together. Kion is shocked to see that his father is finally getting along with Bunga, and the Guard are equally shocked to see Bunga riding atop the king. Timon and Pumbaa are relieved to see their kids back safe and sound, though Timon scolds Pumbaa for worrying. Back at Mizimu Grove, the elephants finish their concert, with Kiara and Nala applauding their hard work. Nala apologizes for Simba's absence, though Ma Tembo is understanding, pleased that they came regardless. Just then, Simba arrives with Timon, Pumbaa and the Lion Guard in tow, apologizing for his late arrival. Bunga causes confusion when he regards himself as brother to the king, and further confuses Kiara by telling her to call him 'uncle Bunga'. Nala questions what happened, though Simba brushes it off as being 'quite an adventure'. He thanks the herd for their patience, though since he missed it, he decides to sing a song dear to his family. Together, the royal family and the Lion Guard sing Hakuna Matata to Ma Tembo's herd, which delights them.