BOOM is the thirteenth episode of the fourth season of the television series Agents of S.H.I.E.L.D. and the seventy-ninth episode overall.
Daisy, Mace and the S.H.I.E.L.D. team must find a way to contain an explosive Inhuman. Meanwhile, Coulson and Mack come face-to-face with Radcliffe’s inspiration for Aida.
At the Playground, Director Jeffrey Mace learns from Jemma Simmons that the super-serum that he has been using to pose as an Inhuman could endanger his health and that he must stop using it. Having to step away from the field, Mace still serves as the public face of S.H.I.E.L.D., arranging the relocation of Inhumans by the Watchdogs. Indeed, the armed group is still very active and soon makes another victim : their leader Anton Ivanov sends Tucker Shockley to expose Senator Ellen Nadeer to a Terrigen Crystal since she could also be an Inhuman like her brother.
However, it turns out that Nadeer is not an Inhuman, unlike Shockley, who undergoes Terrigenesis and uses is newly acquired explosive powers to kill the Senator and her staff. After S.H.I.E.L.D., unaware of Shockley's true nature, sends a team to investigate, Shockley is arrested and brought aboard the Zephyr One, that he nearly takes down before being ejected. Another field mission is set up and successfully captures Shockley in a containment sphere designed by Leo Fitz, locking him in a secure containment sphere, but Mace is seized by the Watchdogs while ensuring the rest of the agents' escape.
Meanwhile, in Caldes de Montbui, Spain, Phil Coulson and Alphonso Mackenzie retrieve Agnes Kitsworth, Holden Radcliffe's former girlfriend. Though Radcliffe left her after failing to cure her from a brain cancer, he never forgot Kitsworth since the Life-Model Decoy Aida was built with exact resemblance to Kitsworth. Coulson and Mackenzie convince Kitsworth to arrange a meeting with Radcliffe, so that S.H.I.E.L.D. could locate and rescue Melinda May. However, Radcliffe in turn persuades Kitsworth that he has a way to save her : the Framework, a whole virtual rebuilding of the real world built by Aida thanks to the knowledge found in the Darkhold. Radcliffe, much to Coulson's dismay, takes Kitsworth with him and connects her body to the Framework. When her consciousness has successfully been downloaded in the Framework, Radcliffe euthanizes her body, wishing to ensure for her an everlasting life in the virtual world.