Two weeks from the end of their experiment, eight bunker members panic when the bunker mysteriously loses power. They are forced to break the number one rule in order to restore basic functions.
Trapped in the bunker with no escape, the team faces a rebooted AI that no longer recognizes them. Forced to re-enter their data verbally, they uncover damning information about each other.
Despite their desperate fight to stop it, a strange disease spreads through the bunker, infecting everyone except one.
A fire breaks out in the bunker's food store, depleting their supplies and sparking intense tensions among the bunker members.
The power and life support systems in Subterranea mysteriously shut down, leaving the bunker members unable to restart them. As oxygen depletes, they slowly succumb to hallucinations.
The bunker members grieve a fallen comrade, coming together for a solemn ceremony to honour their departed. Each person copes in their way as they navigate through the loss.
Chaos erupts in the bunker, with signs pointing to a mole communicating with the outside world. An all-out hunt ensues, but hope takes an unexpected turn when the bunker members make a shocking discovery.
In the finale, a purge sequence gets initiated in the bunker. The occupants fight tooth and nail to stop it but are cornered and under-equipped. Can they survive this?