Following the events from the previous episode, the Lion Guard, Jasiri and Janja follow Azaad to a shortcut through the Outlands, where they meet up with Cheezi, Chungu, and Madoa, who are pleased to see their clanmates again. Madoa explains that Zira and her pride entered the Pride Lands not long after Janja and Jasiri left to find the Guard. The hyenas have been living in hiding ever since, and thus don't know what happened after. Thinking Zira and her pride is still in the Pride Lands, the Guard realize they need all the help they can get, which comes in theform of Jasiri's hyenas and Mzingo's vultures.
Nearing the Pride Lands, Anga reports that a strange lion is on Pride Rock. Jasiri identifies him as Kovu based on a descriptive appearance. With no indication that the rest of Simba's pride is even there, the Lion Guard is about to continue with great haste. Suddenly, Vitani, Kovu's sister, and a group of lionesses stop them in their tracks, warning the "Outlanders" not to invade the Pride Lands. Vitani, clearly the leader of this new group, barks out orders to Shabaha, Kasi, Imara, and Tazama, before launching an attack shouting out the phrase "Till the Pride Lands end, Lion Guard defend!".
Stunned at hearing their own catchphrase, Kion lets his guard down and allows Vitani to attack him. Soon, a battle ensues between the two Lion Guards, with members from each team proving to be evenly-matched against the other. Noticing how similar their strengths are, an idea comes to Ono. He calls for the vulture to distract Tazama, Vitani's Keenest of Sight, while he and Anga assist Kion with Vitani. With Tazama unable to keep watch, Kion is able to knock out Vitani. Having had enough, Kion orders his team to get behind him as he prepares to use the Roar of the Elders on Vitani's Lion Guard.
Suddenly, Kiara appears, calling for her brother to stop. Kion is pleased to see her, but his joy is short-lived when he notices Kovu sliding down the wall behind her. Believing Kovu will attack her, Kion calls for Kiara to move out of the way, but Kiara refuses, blocking him from using the Roar against Vitani's Lion Guard or Kovu. Kiara explains that Zira's Pride has joined theirs, much to Kion's surprise. With both sides calming down, Vitani finally recognizes Kion as Kiara's little brother, though she admits it was hard to do so with his new scar, as well as seeing him surrounded by Outlanders, in which she is also unaware of them being on the Pride Landers' side or not.
Kovu then joins the group, asking Vitani what's going on moments before Bunga does the same. Confused, Kion explains that he and Lion Guard had come to the Pride Lands after learning that Zira was attacking the Pride Lands. Somberly, Kovu reveals to the Lion Guard that Zira has completed her journey through the Circle of Life, much to the Lion Guard's surprise. Understanding her brother's confusion, Kiara tells Kion to return to Pride Rock, offering him to explain everything back there. After thanking Jasiri for her support in the fight, the Lion Guard follow Kiara and Kovu to Pride Rock. There Kion at first reunites with his parents, who realize with worry that Kion still has his scar. But he can assure them both by explaining that even though he will now always have it, he has been healed successfully. When the others arrive, Simba asks if their journey was worth it. The rest of the Guard admit having enjoyed the journey and staying at the Tree of Life where Ono managed to recover his eyesight. Simba then spots a stranger among them and Azaad presents himself to Simba and Nala. The king and queen accept him in the Pridelands, thank him for having brought home safely Kion and his guard and offer him to stay with them. Afterward, Rafiki asks about Makini's whereabouts, noting her absence from the group. Kion reveals she decided to stay at the Tree of Life by becoming Queen Rani's new royal Mjuzi, causing Rafiki to announce that Queen Janna had been right all along: Makini's true destiny was always at the Tree of Life, and not in the Pride Lands as Rafiki had once believed. Before long, the subject of Zira is risen up again, and Rafiki guides them to the lower section of Pride Rock, ready to reveal what happened while they were gone.
Using paintings detailing the story, Rafiki explains that, after the Lion Guard's first encounter with the Outsiders, Zira devised a new plan to take over the Pride Lands. Taking over for Rafiki, Kovu now explains that Zira raised him to believe that Simba and his pride of lions was their enemy. However, after getting to know Simba and Kiara, Kovu realized that Zira was wrong and changed sides. Kiara reveals that, soon after, Zira led an attack on the Pride Lands herself, where she engaged with Simba's Pride. Kiara and Kovu intervened during the showdown between both prides, explaining that they didn't have to fight, with Kiara explaining that, as lions, they are one.
Zira's lionesses, including Vitani, saw that this was true, and joined the Pride Landers. Zira, though, was unwilling to get past her hate, and this ultimately led to her destruction (with her falling to her death, because of her refusal of Kiara helping her). After Zira's death, Simba welcomed the rest of the Outsiders into his Pride, ending the story. In the present, Simba declares that one day, Kovu and Kiara will rule the Pride Lands as king and queen, naming them as his successors, while Vitani made a Lion Guard of her own during Kion and his Guard's absence. Hearing all that they have missed while being away for a long time the Lion Guard soon learn sfrom Nala that they themselves were deeply missed as well, as Bunga and Beshte soon reunite with Timon and Pumbaa, and Basi, respectively.
A montage soon happens, showing the members of the Lion Guard enjoying their return to the Pride Lands and reuniting with the friends and family they had left behind: Anga meets with Hadithi in the skies; Bunga relaxes with Timon and Pumbaa at Hakuna Matata Falls; Ono performs the Hamerkop Family Dance with Kulinda and her daughter Ona, who views Ono as her dad; Beshte reunites with Makuu's crocodiles, his pod and an older Mtoto; and Fuli spends the day showing Azaad around the Pride Lands before troops of baboons catch up and surround them. That night, all of the royal family, including the new prince Kovu, smile at Mufasa as he leaves their sight from the clouds.
All but Kion return to the den, prompting Kiara to sit alongside her brother to see what's troubling him. Kion tells Kiara that seeing her with Kovu reminded him of a "friend" he met back at the Tree of Life. Quickly realizing what is going on, Kiara lightly teases her brother about his "friend" as he tells her about Rani, noting that Kion fell in love with a Queen. Kion goes on talking about Rani, noting that Kiara would like her. Listening to Kion, Kiara detects her brother's sorrow and gets him to confess that he does miss Rani very much. Understanding and supportive, Kiara suggests that maybe Kion could go back to the Tree of Life and Rani someday, believing that their parents would understand Kion's decision.
The following morning, the Lion Guard decide to go into their Lair. However, the lair is occupied by Vitani's Lion Guard, and both teams start arguing over who should be the Lion Guard, with Kion pointing out that his team is real, because they have the Mark of the Guard and the Roar of the Elders. Before both teams can fight, though, Laini rushes into the lair and tells both Lion Guards that there's an emergency at Mbali Fields. After some encouragement from Azaad, both teams head over to solve the problem, working together. Laini takes them to the emergency, revealing it to be Thurston getting the upper half of his body stuck inside a hole.
However, both Lion Guards soon get distracted arguing over each other over what to do. However, Azaad walks over to Thurston and tells him to walk backward out of the hole, solving the problem and shaming both teams. Realizing they won't be able to help anyone by fighting all the time, both teams soon start arguing over which Lion Guard is the best. Hearing this, Thurston suggests they do things the zebra way and have a competition to prove who is the best. After discarding the original Lion Guard test in the Lair, Ono proposes that both teams do a series of challenges to prove which team is the best. Both teams agree to the competition while Thurston starts spreading the word.
The contest is witnessed by the entire Pride Lands, with Rafiki acting as the announcer. The contest is presented as a "best of" five challenges between both Lion Guards, during which the members that represent the roles of Fiercest, Bravest, Fastest, Strongest, and Keenest of Sight will face off against their counterparts to see which one is better. Since Ono's role of Smartest is a newly created role not present in Vitani's Lion Guard, Ono will act as a referee for the contest. The rules establish that the losing side of the previous challenge will get to set the conditions for the next challenge.
As a challenging team, Vitani's Lion Guard gets the first choice. Starting with Strongest, Imara declares that for the challenge, the Strongest of both Lion Guards will push a giant rock with an elephant on top it across Chakula Plains, with the first to reach a tree at the end winning the challenge. Arriving at Chakula Plains, Beshte and Imara face off in the contest as they push Ma Tembo and Zito, respectively. Though Beshte seems close to winning, he soon begins to tire as he gets sunburned. Convinced by Ma Tembo, Beshte runs off to a mud pit to cover his skin, allowing Imara to catch up and win the competition, giving Vitani's Lion Guard the lead on the competition. Beshte makes his way to his friends, who reassure him that he did fine, caring more about his health than him winning.
For the second round, Fuli chooses that the Fastest will compete. Making their way to a canyon, Ono reveals the challenge chosen by Fuli: Fuli and Kasi will race each other across the canyon, loop around, and return to the finish line, with the first declared winner. Starting the race, Kasi is seen using her energy too quickly while Fuli paces herself. Upon reaching the end, Fuli makes a final sprint to the finish line, winning the race and earning Kion's Lion Guard their first victory. While Fuli is welcomed by Azaad and her friends, Kasi makes her way to her Guard in defeat. Declaring that the third round will involve the Keenest of Sight, Ono allows Tazama to make her pick.
Standing in front of a cavern, Ono explains the Keenest of Sight challenge: both competitors will use their keen eyesight to locate Laini, who has hidden in a dark cave. Inside the cave, while Anga struggles to see around her, Tazama uses her night vision and finds Laini quickly. Returning outside, Laini declares Tazama the winner of the contest, putting Vitani's Lion Guard back in the lead. While Anga apologizes to her team, Bunga reassures her, noting that the Bravest is up next, and he gets to pick. For the fourth round, Bunga reveals he planned a series of tests for the Bravest challenge.
The Bravest of both teams will run through Maumivu Thorn Patch, cross Urembo River with Makuu's float, and then climb up Mekundu Cliffs, with the winner being the first to grab the baobab fruit from a tree at the top of the cliffs. Though clearly shaken by the magnitude of the test, Shahaba tells Bunga she is not afraid. The challenge begins, and both cross the thorn patch quickly. However, at Urembo River, Shahaba hesitates on seeing the crocodiles while Bunga crosses them. Though Shahaba soon jumps over the river, Bunga quickly reaches the top and grabs the baobab fruit before the branch supporting Bunga breaks, sending him to the ground with the baobab fruit.
After four tests, Ono declares both teams to be tied up with a score of 2-2, and it all comes down to Kion against Vitani. Given the choice, Vitani calls for a mashindano to prove who is the fiercest. As the Pride Landers start chanting for the mashindano, an appalled Kion tries to tell Vitani she won't stand a chance against him because he has the Roar. However, Vitani says she doesn't need the roar, telling Kion she is already fierce enough to lead the Lion Guard without it. Kion is left amazed at her courage, realizing she knows the lesson it took him a while to learn. Kion remembers Askari's words from before: "Only one who is willing to let go of the Roar completely...can truly master it."
Realizing she is right, Kion forfeits the last challenge, declaring that Vitani has proven herself to be the Fiercest by choosing to challenge him even without having the Roar. As a result, Vitani's team wins the contest, making them the new Lion Guard of the Pride Lands. Kion then turns to Vitani and, giving her his blessing, passes on the Mark of the Guard and the Roar to her. Surprised, Vitani tests out the Roar of the Elders for the first time as the Pride Landers cheer her on, officially welcoming them as their new Lion Guard. Meanwhile, Kion and his friends watch as their Marks of the Guard disappear from their shoulders, somberly accepting that their time as the Lion Guard has come to an end.
Suddenly, Askari appears in the sky in front of everyone, including both Lion Guards and Pride Landers who are stunned by Askari's appearance. Askari tells Kion that he has truly mastered the roar by letting it go. Confused, Kion asks why he would still need the Roar if he's no longer the leader of the Lion Guard. However, Askari tells Kion that there's another place that could use the Roar's help, causing Kion to realize that he's talking about the Tree of Life and the Night Pride protecting every animals around this place. At that moment, the Mark of the Night Pride that was given to Kion by Queen Janna before her death reappears on Kion's right shoulder.
Turning to his friends, Kion asks them if they all want to join him by helping Queen Rani protect the Tree of life. Happy to go back, Kion's friends accept the offer as the Mark of the Night Pride replaces their Mark of the Guard on their bodies. Approaching Kion, Vitani asks what it means to truly master the Roar. Telling her to watch, Kion explains the meaning of it by summoning the Roar of the Elders and, proving his mastery of the power, lifts the entirety of Pride Rock off the ground and holding it aloft in the air as the Pride Landers watch in surprise. After returning Pride Rock to the ground, Kion listens as Vitani utters his catchphrase "Hevi Kabisa" in shock, but also in admiration, wonder, and amazement.
Sometime later, the Pride Landers and the Tree of Life's inhabitants alike are seen gathered outside the Tree of Life to witness Kion's wedding ceremony to Queen Rani as well as his ascension to being King of the Tree of Life. Before the ceremony begins, Kion approaches Rani, who admits to him with an honest dreamily smile at him, that she's glad to have the Roar finally returned back to the Tree of Life. Agreeing, Kion affirms her that this time it's here to stay here, as both look forward to ruling the Tree of Life together. Makini then anoints Kion's forehead, drawing a blue-colored v-shape on his head, officially declaring him as the new King of the Tree of Life as the crowd erupts in joyful cheers. She then embraces her parents Fikiri and Kitendo in reunion. Pinguino tells Thurston that Kion is as fierce as a penguin, whilst Thurston replies he taught the lion all he knows. When Kion tells Rani they'll make a great team, but she responds that they already do, meaning their two teams working together to fight against enemies. Then both roar together to emphasize their reigning together. Meanwhile, Askari, Janna, and Mufasa are seen appearing in the sky, looking down at the ceremony in happiness as the Great Lions of the Past roar with approval and pleasure one last time.