Episode 4 of the new season of *Invasion* opens with the kids speeding through Folkestone, on their way to cross into France. President Benya's urgent message about the coordinated assault on the carrier ships plays on an endless loop over the radio. When the group arrives at the border crossing, they notice everyone has stepped out of their vehicles, eyes fixed on the sky. Having been lost in their own world with music blaring in the car, the kids were oblivious to the unfolding chaos. Sensing danger, Jamila urges Monty to abandon their current route and opt for the tunnel into France instead.
They abandon their car near the tunnel entrance and slip past the guards unnoticed. Initially hesitant, Monty frets over the risks, especially to Penny's safety, but eventually relents, persuaded by Jamila's determination. As they venture deeper into the tunnel, the distant sound of explosions echoes through the air, signaling the attack's peak. The group, now anxious, wants to retreat, but Jamila stands her ground, insisting they press on toward Caspar, their sole beacon of hope.
Meanwhile, at the hospital where Caspar is under close observation, patients are tuned into the radio, where the announcer speculates that the attack marks a significant turning point in the ongoing conflict. Beyond the hospital's general ward, neurologist Esmee steps into a highly secured zone. Inside, a roomful of children sit at desks, engrossed in drawing. The nature of their artwork remains ambiguous, but it hints at a possible connection to signals emanating from Caspar's brain, projecting images directly into the children's minds—or so it appears at this juncture.
Gabriel, Esmee's colleague, doubts Caspar's chances of recovery, considering him beyond medical help. Yet, Esmee clings to hope, believing he will awaken someday. Ahead, the kids stumble upon a gruesome scene: a group of soldiers lies lifeless on the tracks. Suspecting alien involvement, they deduce these men were part of a reconnaissance team sent to explore the tunnel's depths.
Almost immediately after discovering the bodies, they realize Penny is missing. Soon after, faint growls emanate from the shadows, revealing an alien advancing toward them. Monty's foot gets caught in the terrain, rendering him immobile. But just as the alien closes in, it suddenly powers down and collapses, mirroring the events of the previous episode.
Penny reappears shortly after, explaining she had been scouting alternative paths for the group. She had found one, albeit a perilous one, littered with what appeared to be hibernating aliens. Whether these creatures are merely dormant or truly deceased remains uncertain at this point.
After trekking a certain distance, Jamila's attention is caught by peculiar patterns swirling in the water stream. With a sense of foreboding, she places a bottle amidst the strange phenomenon and jumps to the conclusion that it must be some kind of alien signal being transmitted back to their mothership. This ominous discovery coincides eerily with the dormant aliens left behind suddenly glowing faintly, and a special student within the secure zone rushing to inform Esmee about even more perilous aliens on their way.
Esmee is shown a photograph of a wolf, a harbinger that the new swarm of aliens will be far more ferocious. And true to the warning, chaos erupts as an ambulance careens into the hospital. The driver, with barely enough time to breathe, alerts Esmee about the impending alien onslaught. Back in the tunnel, the dormant aliens also stir from their slumber. They begin to advance towards the group, who hastily barricade themselves behind an iron gate. Monty, ever the calm presence, reassures Penny, who is reeling from the recent events, and together they dash towards safety as the evolved aliens start to breach the gate.
The group's confidence and unity waver with each passing moment as they desperately search for an escape route. Tensions flare, leading to an in-fight between Alfie and Monty. Alfie accuses Monty of being the school bully who mercilessly tormented Darwin. However, the conflict is resolved when Monty, with a raw vulnerability, opens up about his frustrations with the changing times.
The children stumble upon a crashed train and soon realize that the end of the tunnel is within reach. Jamila experiences a vision where she converses with Caspar as if he were right there beside her, a feat made possible by his mental prowess. Caspar discloses that his physical body lies nearby in a hospital, while a part of his consciousness resides with "them"—the aliens. Together, they steel each other for the ongoing struggle, vowing to emerge victorious. Caspar's role becomes paramount as he now has direct access to the alien minds.
The kids discover that the tunnel's exit has been blocked by the military, who have rigged it with explosives and are poised to detonate. The children scream for help just in the nick of time, and the soldiers respond, aiding them in their escape. The aliens nearly reach the end, but are obliterated by the blast.
Everyone at the hospital has already evacuated, leaving behind only Caspar, who remains unconscious in a coma. The group, now even more resolute, is determined to locate Caspar and tip the scales in humanity's favor in this interstellar war.
