The Liberation of Leo Fitz was an elaborate masquerade orchestrated by Jemma Simmons in order to trick Alphonso Mackenzie into releasing Leo Fitz, who had been imprisoned in the Lighthouse on Daisy Johnson's orders, so they could investigate his lead on General Hale.
Due to being exposed to a lot of pressure while unsuccessfully trying to find a way to compress the Gravitonium so S.H.I.E.L.D. could seal the Fear Dimension rift which had opened in the Lighthouse, Leo Fitz experienced a major psychic split. This caused his dark personality from the Framework, The Doctor, to manifest. The Doctor kidnapped Daisy Johnson to forcefully remove her Inhuman Control Device, restoring her powers she had to use to compress the Gravitonium. Although the operation was successful and Johnson was able to close the Fear Dimension, she was traumatized by the whole episode and ordered Fitz, who had returned to his normal self, to be locked up in a cell.
Later, Melinda May came to see Fitz in his cell to have his insights about General Hale, secretly a leader of HYDRA who had kidnapped Phil Coulson. Fitz suspected that Hale was after an old HYDRA weapon and suggested to be temporarily released so he could assist in the search. However, Johnson categorically refused to set him free. Fitz's wife Jemma Simmons, who supported her husband, unsuccessfully tried to convince Johnson, and later Alphonso Mackenzie, to release Fitz. As she believed Yo-Yo Rodriguez's story about being invincible because of what they had seen in the future, Simmons began planning to release her husband so the three of them could conduct their own investigations.
Yo-Yo Rodriguez asked Alphonso Mackenzie to come to Leo Fitz's cell, where Jemma Simmons awaited them with some equipment. Simmons explained to Mackenzie that, much like Rodriguez, she believed that she could not be killed, as she knew Deke Shaw, who they had encountered in the future, was her grandson. As Mackenzie looked at Fitz, Fitz answered that he had no idea what Simmons had in mind.
Simmons further detailed the experiment she intended to carry on: she filled three beakers with water and one with a highly toxic transparent chemical and asked Rodriguez to move the beakers while Simmons was not looking. Simmons would then drink three of them and, given that she could not die, she would only drink the ones containing water. Upon hearing this, both Mackenzie and Fitz were horrified and advised Simmons against the whole plan.
As Mackenzie and Fitz watched in anxiety, Simmons drank the first two beakers without being harmed in any way. However, once she took the third beaker despite Mackenzie threatening to hurt her in order to stop her, she collapsed on the ground and screamed in pain. Panicking, Mackenzie asked Fitz what he should do to save Simmons and Fitz asked for being released so he could help. Mackenzie agreed and opened the door, enabling Fitz to run for medicines to help his wife.
However, the whole situation appeared to be a massive trickery as Rodriguez used her superhuman speed to lock up Mackenzie in the cell. As Fitz returned, Simmons revealed that she actually was perfectly fine and had faked her poisoning. Upset at the idea of having been kept in the dark the whole time, Fitz nonetheless hugged Simmons in relief and complimented her for her acting performance. However, Simmons explained that she had not lied on the whole experiment: the final beaker, which she did not drink, did contain a toxic chemical which could have killed her. According to Simmons, this proved that her theory was right.
Rodriguez apologized to Mackenzie for siding with Fitz and Simmons and leaving him in lockup. Although a minor incident occurred when Rodriguez accidentally shot at the wall because of her lack of control on her new prosthetic arms, Simmons, Rodriguez and the now free Fitz left to carry on their investigations.
Taking advantage of the fact that there was no one to stop them, Leo Fitz, Jemma Simmons and Yo-Yo Rodriguez took an autopiloted Quinjet to Herefordshire, England, in order to infiltrate an abandoned HYDRA facility Fitz had identified as a place of interest for General Hale.
Alphonso Mackenzie was eventually released by Agent Piper, who found him and feared that Fitz had returned to his dark personality. Mackenzie explained that Simmons and Rodriguez were the one to blame for the liberation of Fitz, but before they could try to locate them, the rest of the S.H.I.E.L.D. team returned to the Lighthouse with a heavily wounded Deke Shaw. Mackenzie informed his colleagues about what had happened, but they were unable to know where Fitz, Simmons and Rodriguez were until S.H.I.E.L.D. attacked the HYDRA Preparatory Academy.