Alit lived on Floor 0507 of a Mondasian colony ship. Following the arrival, and subsequent attack, of some patients from Floor 1056, (TV: The Doctor Falls) Alit was sent by her parents to live in a large farmhouse on the floor for her protection, (PROSE: Alit in Underland) that also served as the home for several other children and adults, including Hazran. During a ride with some other children on a horse-and-cart, Alit watched the chained-up patients in the fields. That night, she watched the patients through her bedroom window when they attacked the farmhouse. The next morning, Alit was skipping through the fields while the adults chained the patients to crucifixes, when she felt an earthquake and saw bright light emerging from the ground. A shuttlecraft then blasted through the ground, before crashing back down, barely missing Alit. The Cyber-converted Bill Potts emerged, carrying an unconscious Twelfth Doctor, alongside the Master, Missy and Nardole, the last of whom greeted her. (TV: The Doctor Falls)
The following night, Alit followed the Master and Missy out of the farmhouse and through some woods, before arriving at the crashed shuttlecraft. Deciding to return to the farmhouse, she was nearly captured by a patient. Alit quickly fled down into the superstructure walkway that the Master and Missy had travelled down to, and decided to join them in their journey to Floor 0508. After eventually finding a service lift to Floor 0508, Alit entered it in order to activate it. When the patient that tried to attack her on Floor 0507 caught up to the trio, Alit hid in the service lift while the two Masters fought it. Afterwards, the trio travelled to Floor 0508 alongside the newly-reprogrammed patient (who Missy referred to as "Topknot").
Spending the majority of the next day riding various pieces of automated farming equipment, the group eventually found a network of storage silos, only to encounter a group of CyberNeomorphs. Alit and Missy escaped the Cybermen, after Missy and the Master caused a distraction, into a grain store, where Missy captured some rats and held them captive in small cages around her and Alit's necks; these tricked the Cybermen's lifesign scanners into registering them as lifeforms with three hearts, buying the pair enough time to find Topknot and escape to a weather control centre. After Missy sent a swarm of Cybermats back to Floor 1056 and forced a rainstorm to occur, Missy freed the Master while Alit acquired three pairs of rubber boots. This allowed the trio to escape the Cybermen; after using Topknot as bait, the Master used his laser screwdriver, combined with the rainstorm, to generate an electrical blast that destroyed the Cybermen but didn't kill the Masters or Alit as they were wearing the rubber boots. Returning to Floor 0507, Alit noted that Missy could have also stopped the Cybermen, but chose not to. (PROSE: Alit in Underland)
Two weeks later, Alit chose to give Bill, who had been sleeping in a barn, a mirror, so that she could see her Cyber-converted form. Afraid, Alit left, only to run into the Twelfth Doctor, who gave her a jelly baby before she left. In preparation for the Cybermen's attack, the Doctor attempted to explain his intentions for her role in the battle with toys but ultimately gave up. That night, when the Cybermen attacked Floor 0507, Alit confronted a large group of Cybermen and threw an apple at them, shortly before Nardole triggered a fuel explosion underneath them. She eventually evacuated, along with the other humans, with Nardole and Hazran to Floor 0502, where Nardole explained to her that although most of the Cybermen were dead, a few survivors remained and would likely try to find them again. (TV: The Doctor Falls) Ultimately, Nardole succeeded in protecting Alit and the other humans. (PROSE: Twice Upon a Time)