The episode kicks off with Dr. Ramona Pamani (Sakina Jaffrey) administering a serum to Devin Brewer (Sam McCarthy) and his companions, a potion designed to shield them from being encased in cocoons or pods. As she elucidates its mechanism, she hands one dose to Anthony Brewer (David Schwimmer). Prior to securing them in the subterranean hatch, her voice tinged with regret, she offers an apology.
It isn't long before they discover the main chamber, a cavernous space brimming with cocoons and pods. As Cece Brewer (Jayden Bartels) administers the serum to Anthony, who emerges from his pod, the spaceship reappears on the horizon. The group hastily evacuates the chamber, adhering to Ramona's instructions.
Officer Morales (Esteban Benito) confronts Jen (Ana Ortiz) with the news that Alex's (Francesca Noel) ankle monitor has gone dark, a revelation that leaves her visibly shaken.
Anthony awakens in the underground sanctuary, where the children recount the tale of the serum and their confinement. Their dire predicament dawns upon them, until Anthony recalls that the hatch had opened during his initial visit to the fort. This revelation prompts Trey Jiminez (Stony Blyden) to confess that he had jammed the bolt cutter into the transformer. Trey's expertise in electrical engineering becomes invaluable as he deciphers the facility's blueprints and locates the power source.
Anthony then devises a daring plan: using the facility's solitary Tyvx suit to disable the spaceship while the others flee once Trey cuts the power. Cece and Devin protest, but Anthony proceeds regardless. In a tense moment, he narrowly avoids disaster and successfully disables the ship. Meanwhile, Trey executes his part, severing the power. However, a close call damages the canister, forcing Anthony to remain behind to stabilize it. The others escape and await his return at the hatch. Anthony arrives with Matty Brewer (Christopher Paul Richards) and the other encased children, narrowly escaping as the hatch slams shut. To their astonishment, a highly distressed Jen arrives on the scene.
Hannah Parker (Eloise Payet) engages in conversation with Devin, while Anthony speaks with Matty. Matty's memories of the past begin to surface, and Hannah recalls meeting Devin. Jen's visit to the Brewer household is fraught with difficulty, particularly as she struggles to converse with Matty and keep his return a secret. Anthony is intent on locating Ramona and addressing the spaceship beneath Fort Jerome, but Jen is initially reluctant. However, she eventually relents.
As Anthony and Jen venture into Ramona's warehouse to raid it, Matty and the other podded children find themselves at the Brewer house, accompanied by Cece, Devin, and their friends. Restless and eager to stretch their legs, the podded kids express their desire to venture out, much to Cece's chagrin. However, she relents when they devise a plan to split up and explore.
Meanwhile, at the warehouse, Anthony and Jen encounter Ramon, who is in the midst of reviving her father, Dr. Avi Pamani (Sendhil Ramamurthy). Upon his revival, he undergoes a transformation into a malevolent organic substance and nearly claims Anthony's life, but Jen intervenes just in time. This harrowing experience serves as a stark reminder that Matty and the other podded kids could undergo the same harrowing transformation.
Elsewhere, Sameer (Arjun Athalye) undergoes the transformation after dining at CJ's (Elijah M Cooper) parents' restaurant. Hannah's transformation occurs while she is with Devin, prompting her to attack him until she is struck by a car. This narrow escape allows Devin to reach Frankie (Galilea La Salvia) before Trey succumbs to the transformation. At the Brewer house, Cece and Alex are flipping through old family photos with Matty when he too undergoes the terrifying change. Attempting to attack them, they narrowly escape his clutches.
Outside, they bump into Devin and Frankie, only to find themselves cornered by four of the previously podded kids who have undergone the transformation. Jen and Anthony return home just as the evidence of Matty and the others' transformation becomes undeniable, along with the revelation that Devin and Cece have been podded. This grim discovery prompts Anthony to realize that they must release the ship to prevent further disaster.
Upon returning to the fort, Anthony and Jen are set upon by two of the transformed kids. Jen manages to incapacitate one with a dart, while Anthony subdues the other with a small canister of the serum. However, a third attacker catches them off guard, causing Anthony to lose his canister and Jen to expend her last serum dart. Despite the odds, they make it to the room housing the entrance to the underground tunnel and successfully release the ship. As it escapes, it creates a solar flare-like explosion overhead, eventually dissipating into the sky.
Anthony catches sight of Matty at the fort and is heartbroken to learn that he is leaving for good. Despite Anthony's pleading, Matty insists that he must go, but encourages Anthony to be there for Cece and Devin. Matty joins the other podded kids, revealing that the ship is taking them with it. After bidding farewell to their newfound friends, Cece and Devin return to St. Agnes. Trey returns home and regurgitates the black oily substance, leaving a haunting cliffhanger as the episode draws to a close.
