Broken Promises is the ninth episode of the fourth season of the television series Agents of S.H.I.E.L.D. and the seventy-fifth episode overall.
Though Coulson and May are growing closer, Coulson remains unaware of the dark secret May is hiding beneath the surface. Meanwhile, Aida is unrelenting in her search for the Darkhold.
At the Playground, Mace summons an emergency meeting with the top S.H.I.E.L.D. agents in order to plan the way of dealing with the Darkhold. They also need to erase Aida's memory since the android read the Book of Spells to rescue Phil Coulson and Leo Fitz who were trapped between dimensions. Both Holden Radcliffe and Fitz are reluctant at the idea but finally agree after Alphonso Mackenzie voices his concerns about a possible "robot rebellion". Shortly after, Radcliffe and Fitz take a team of S.H.I.E.L.D. agents to the Radcliffe Residence. However, the situation goes south when Aida, who had been turned off by Radcliffe, suddenly wakes up and assaults them, knocking everyone in the room before escaping. In shock, Fitz discovers the body of Nathanson, who was killed by Aida after he discovered that the android had kidnapped Melinda May and was keeping her prisoner.
Fitz and Radcliffe return to the Playground, where Radcliffe explains to Coulson and Mackenzie that the Darkhold is likely the cause of Aida's rebellion, giving her the desire to be a living being. Aida soon attacks the Playground and demands to be delivered the Darkhold. When Coulson refuses, Aida hacks into the base's systems and shut it down. Mackenzie teams up with Elena Rodriguez while Coulson and Melinda May's Life-Model Decoy are confronted by Aida, who quickly knocks Coulson out and turns May's LMD off. She then locks them in a room. Meanwhile, Fitz and Radcliffe struggle to restore power in the Playground and Fitz hypothesizes that the Darkhold gave Aida emotions and free will.
Mackenzie and Rodriguez then have to face Aida's assaults, who remotely took control of the S.H.I.E.L.D. Quinjets in order to keep them from coming after her. She also monitors May's LMD's eye camera and thus learns from Coulson that the Darkhold is hidden in Mace's office. She finds it and tries to exit the Playground, but is told to stop by Fitz and Radcliffe, who are soon joined by Coulson and May's LMD, and later by Rodriguez and Mackenzie, who uses his Shotgun-Axe to behead Aida. Coulson reclaims the Darkhold and Fitz keeps Aida's head in order to know why she rebelled.
In parallel of all those events, Vijay Nadeer, the brother of the anti-Inhumans Senator Ellen Nadeer, wakes up at their residence and joins his sister for breakfast. It turns out that Vijay is the Inhuman that Jemma Simmons helped with his Terrigenesis during her secret assignment. While Simmons discuss his fate with Quake, Burrows takes Quake to Mace's office where they talk about the events of Los Angeles and how Quake suddenly turned from a feared vigilante to a national hero. After a tense exchange, Quake and Mace agree to work together in order to counter Nadeer's offensive against S.H.I.E.L.D. Therefore, Mace, Quake and Simmons decide to rescue Vijay Nadeer from his sister. Indeed, Vijay is in danger since her sister is working with the Watchdogs and intends to eliminate him.
Simmons tries to infiltrate Ellen Nadeer's office, but her assistant recognizes her as the S.H.I.E.L.D. scientist who was enlisted to help Vijay and, on the Watchdog officer Tucker Shockley's order, attacks her, but Simmons manages to knock him out. Meanwhile, Ellen Nadeer reveals to her brother the presence of the Watchdogs who came to kill him. However, at the last moment, Ellen breaks down and orders Shockley to spare the life of her brother. Later, Shockley confronts her about her decision but they are interrupted by Mace, Quake and Simmons. Nadeer orders them to leave, which they do, but quickly return after hearing a gunshot due to Shockley trying to kill Vijay. It turns out that his Terrigenesis gave him superhuman reflexes that enable him to fight back against the Watchdogs. Ellen Nadeer and the S.H.I.E.L.D. agents join him and Ellen persuades Vijay to go with her. They take an helicopter with Shockley and Ellen finally shoots him before dumping his body into the ocean, where he undergoes Terrigenesis once again.
At the Radcliffe Residence, Radcliffe toasts to his fallen Aida in company of another Aida. Radcliffe actually engineered May's kidnapping and replacement by a LMD and Aida's rebellion in order to get the Darkhold for himself and achieve his immortality dreams.