In The Garden, Hope Diyoza tells Echo and Gabriel Santiago that she has the Anomaly Stone code for Bardo from someone she knows on the planet, referring to Levitt.
In Welcome to Bardo, Levitt makes his first appearance in the flashbacks and oversees Octavia's Memory Capture (M-Cap). He befriends her in the process. He is revealed to have helped Octavia escape to Sanctum and comforts her when Bellamy is apparently killed. Levitt is also revealed to have been the one to have left the note in Hope's arm. In the present, he is not in M-Cap when Echo, Hope and Gabriel arrive looking for their friends.
In Nakara, as Diyoza, Hope, Octavia, Echo and Gabriel prepare to enter the Anomaly Stone room, Octavia spots Levitt down the hall, now working as a janitor. Levitt silently shakes his head at them and explains to Octavia that there are a dozen Disciples in the Stone room waiting for them who will kill themselves to stop the group from getting back to Sanctum. Levitt instructs the group to head to the surface instead where the Disciples won't follow them as its not survivable for long. Octavia questions Levitt's new profession which he states was worth it and he is still on the code breaking team as they need him too much for that. Levitt states that it was worth it to him and orders Octavia to punch him again and run. After caressing Levitt's face for a moment, she knocks him out and the group follows Levitt's instructions to run though Gabriel hesitates for a moment.
In The Flock, Levitt is assigned to help with the group's training three months before the present. Diyoza confronts Levitt about how the surface is uninhabitable, but Levitt explains that it can be survived for an hour or two and he just needed to buy some time to find another solution. Though Diyoza is dubious of Levitt due to his many jobs, he explains that he was chosen due to his experience with Octavia in the M-Cap and Anders himself will be overseeing their training, something that is extremely rare. Levitt gives them some advice before they are interupted by Anders. Levitt tries to give Anders advice on training the group based on his experiences with them, but Anders brushes him off.
Levitt helps with many aspects of Hope, Diyoza and Octavia's training, running simulations through their minds and running tests with weapons with them. When Echo asks about a biohazard warning, Levitt explains that the room holds Gen-9, the substance that wiped out the native Bardoans, though the Disciples would never dare use it as just a small amount could wipe them all out. After Hope fails the final test, Levitt sorrowfully informs her of this and watches as Echo decides to have her banished to Skyring for five years.
Throughout these events, Levitt continues to grow closer to Octavia leading to the two flirting in her room. The two eventually kiss and have sex with each other.
In A Little Sacrifice, Echo states that she has a plan that she forced Levitt to help her with. After hearing this, a concerned
Octavia rushes to check on Levitt, finding him beaten and bloody. Levitt tearfully states that Echo killed two people in front of him and he broke. Clarke stops Octavia from releasing Levitt, stating that they need to know what Echo is planning. Levitt is stunned to see Clarke, recognizing her as the Key. Levitt reveals the he helped Echo get Gen-9 and she intends to deploy it in the central humidification system on the Machine Level. Levitt admits to telling her how to do it and recognizes Raven Reyes from her understanding of what he means. Levitt begs them to release him so that he can get help to stop Echo, but she sadly gags him again in order to stop Echo without getting her killed. As Octavia leaves, Levitt desperately calls after her.
In Etherea, a battered Levitt is assigned to run M-Cap on a Disciple experiencing PTSD from the explosion that apparently killed Bellamy Blake. Levitt defends the continued need for Clarke and her friends due to them having the Key and reassures Shoana that he is alright. Going through the Disciple's memory, Levitt suddenly notices something and upon closer examination, realizes that Bellamy was blown back through the Anomaly by the explosion and is still alive.
In The Dying of the Light, Cadogan brings Madi Griffin into M-Cap where Levitt greets her and introduces himself. Levitt reassures the nervous Madi and straps her into the machine. As Levitt gets her hooked up to the machine, Madi reveals to Cadogan and Levitt that Gabriel had told everyone that Jordan had discovered from the Bardoan texts that it's not a war but a test that someone has to take. Cadogan dismisses the idea that it's a test, though he claims that he would welcome one instead of a war where his "children" have to die.
Levitt begins the procedure, using Madi's sketchbook to help guide her but has no luck. Madi claims not to remember anything about the woman in the drawing and Cadogan reassures her that they will figure it out together. Madi tells Cadogan that she's not doing it for him but in order to save her friends and family. Levitt informs Cadogan that that that particular memory isn't registering in any of the areas that memory is typically stored. However, Cadogan is sure that those memories are in her mind somewhere. Levitt warns that he is going to have to search much deeper into her cerebral cortex which is extremely dangerous and something that he has never done before. Cadogan states that Levitt is the best and he trusts the young man "for all mankind." Levitt reluctantly nods in agreement.
Levitt is able to find Becca Franko's memory of talking with Callie, but the image disappears. Cadogan orders him to get it back, but Levitt states that it is just a fragment of memory and it is difficult to get to as it is an entirely different pathway from normal memories. Cadogan refuses to let him stop, wanting to see his daughter again. Levitt warns Madi that if he pushes deeper, he might be able to find more of Becca's memories, but it's risky. Cadogan orders him to continue as they need her memories intact and reassures Madi. Despite his concern, Levitt continues bringing up more of the memories, including images of Lexa and A.L.I.E. and Becca arguing with Cadogan.
Madi suddenly stops them, telling Levitt that she saw Becca's memory of going to "the other side" and stating that Cadogan isn't ready. As a result, Madi is done helping them. Cadogan admits that he had a disagreement with Becca a long time ago, but insists that Madi is only seeing Becca's side of the story. Cadogan admits that Becca may have once been right, but he feels that after centuries of improving and preparation, they are ready. Madi refuses and begins struggling despite Levitt's worries that she is hurting herself. Cadogan quickly calls in guards to restrain Madi. Horrified, Levitt refuses to continue, stating that they need to do it another way, but Cadogan is sure that there is no other way. Feeling that Levitt is too close to this, Cadogan dismisses the young man and orders Shona summoned instead. Levitt reluctantly leaves, turning back for a second to watch Madi's continuing struggles and walking through a line of Disciples guarding M-Cap.
Making his way to the Stone room, Levitt orders the Conductor to bring over the people from Earth who had swallowed the nano-tags, claiming that Cadogan had changed his mind. Levitt presses the Conductor who reluctantly agrees and begins the extraction, stating that it will take her a few minutes. However, Levitt becomes concerned when the Anomaly fails to appear and the Conductor explains that as part of war preparations, they had moved it to a strategically advantageous location. As a result, Clarke and Octavia appear in the oxygen plant surrounded by Disciples and are captured.
Levitt makes his way to the prison area and begins working on opening the door, claiming that the eye scanner is broken again. Levitt attacks the two Disciples and quickly overpowers them before resuming his work on the door. Levitt makes his way to Clarke and Octavia's cell and releases them, apologizing for taking so long and admitting that he doesn't have a plan, having figured that that was their specialty. Levitt warns that using the armor cloaked won't work with too many Disciples with helmets around and Clarke decides to create a distraction by releasing Sheidheda.
Walking through the corridor near M-Cap, the group finds many slaughtered Disciples and no sign of the Dark Commander. Levitt is horrified by the carnage as he grew up with them, but Octavia tells that that's war: it looks exciting in holograms, but the reality is much worse. Reaching M-Cap, Levitt goes in first as the Disciples won't see him as a threat, but they find it to be empty aside from an unresponsive Madi. Realizing that something is wrong, Levitt accesses M-Cap's history for answers. As Clarke desperately tries to get Madi to respond, Levitt discovers that while there is still neural activity, Madi's brainstem show signs of a massive stroke. Levitt sadly tells Octavia that while Madi is conscious, she can't move anything. Levitt reveals to Clarke that the areas of Madi's brain responsible for voluntary movement have been destroyed and her condition is irreversible, offering his sincere condolences.
Clarke and Octavia prepare to mercy kill Madi rather than let her live in such a state, but Levitt interrupts them before Octavia can pull the trigger. A horrified Levitt reveals that Cadogan got the code from Madi's mind and displays Becca's memory of inputting it into the Anomaly Stone. Clarke is enraged that Cadogan got the code and abandoned Madi to die with Octavia agreeing that if it really is a test with one man representing the entire human race, it can't be Cadogan. Levitt states that they can still stop Cadogan, but they must leave immediately. Octavia questions if Levitt is sure about helping them as he has wanted this his whole life, but Levitt simply states that before meeting Octavia, he didn't have a life. After Clarke says goodbye to Madi, the three depart to stop Cadogan.
In The Last War, Levitt leads Clarke and Octavia onto an elevator to the Stone room, warning them that Cadogan's personal unit will be with him guarding the door. Undeterred, Clarke pulls out two grenades, upsetting Levitt that more killing is the answer. After Octavia confirms that its what they do, Levitt muses that maybe they don't deserve to Transcend. After Clarke single-handedly kills a dozen Disciples guarding the Stone room, Octavia hands Levitt a rifle while she takes a sword, but they find the Stone room empty and the Anomaly Stone transformed into a ball of light and Levitt realizes that they are too late.
After Clarke enters the light in order to stop the test, Levitt paints Octavia's face in the hallway outside in preparation for the battle to come. Levitt reminds Octavia that if Clarke can't stop the test, they are merely buying time for Wanheda to be the witness for the human race. Octavia asks if Bellamy will get to Transcend if Clarke succeeds, but Levitt tells her that she won't as The Shepherd's Passage states that only the living shall Transcend while death is the end for everyone else. Octavia jokes that she must've slept through that class and notices Levitt get solemn as he arms himself with his rifle and asks him what's wrong. Levitt points out that if Clarke does take the test, then either way, Transcendence or extinction, today is the end. Levitt admits that he would've liked to live a little first and Octavia agrees with him.
Levitt and Octavia's conversation is interrupted by the arrival of a cloaked Raven and Echo who are confused by the carnage. Octavia informs the two that they were responsible for the carnage, that Cadogan had "worse than killed" Madi and that Clarke had gone in order to stop him. Levitt questions the two on how they're sure that they weren't followed, but Raven reassures him that the Disciples have their hands full with Wonkru. Levitt is horrified that they had brought an army to Bardo, but Echo explains that Wonkru isn't there to fight but to act as a distraction in order to get them inside to kill Cadogan. However, Levitt points out that the Disciples don't know that and that it would be "worse than bad" if Clarke is unable to stop the test to determine the fate of the human race while the rest of the human race is fighting a war. If they fail the test, the Transcended will send Gen-9 to wipe out the human race which Levitt derisively states that Echo understands. Echo apologizes for her earlier torture of Levitt, stating that she wasn't herself. Octavia interrupts the argument as they need to stop the war and runs off with Levitt and Echo while Raven remains behind in order to help Clarke.
Reaching the oxygen farm, the three discover Sheidheda trying to provoke a battle between Wonkru and the Disciples. Racing into the middle of the field, Levitt disarms himself and both sides hold their fire. Levitt announces to the gathered people that it's not the Last War and they don't achieve Transcendence through violence. Levitt explains that Cadogan was wrong and that they are all being tested right now and attempts to convince both sides to put down their weapons. However, in order to stop Levitt, the Dark Commander opens fire and shoots him in the back, causing Wonkru and the Disciples to begin fighting.
As Levitt lies in the middle of the field, mortally wounded, Octavia rushes to his rescue with Echo and the two women drag Levitt into the trees, although Echo is also hit in the process. Octavia applies pressure to Levitt's wound as Hope and Jordan rush to their aid. Levitt tells Octavia that they need to stop the war and that she can do it. With Echo also near death from her injuries, Octavia orders Hope and Jordan not to let Echo and Levitt die as the dead don't transcend before rushing off to stop the war.
After Indra kills the Dark Commander, the fighting ceases and Octavia makes a speech to both sides, observed by both Raven and the Judge, urging them to stop fighting before returning to Levitt's side. Near death, Levitt compliments Octavia's speech and she urges Levitt to stay with her and Echo's heart stops beating. Octavia has Hope pump Echo's heart in order to keep her alive as both sides decide to stand down and the Judge becomes convinced that humanity is worthy of transcendence. As Hope desperately tries to keep Echo alive, she suddenly transcends, followed by Levitt who is amazed at the sudden lack of pain.
After Clarke, the only one not to transcend, returns to Earth, the Judge reveals that her friends have chosen to return to human form to live out the rest of their lives in peace on Earth. When Murphy draws everyone's attention to Clarke, Levitt smiles at her from where he is sitting holding hands with Octavia and joins the others in rising to greet Clarke.