It's a typical Friday night eviction on Big Brother. Except it's not a typical evening; there are reports of disturbances and riots all over the country. BB Producer Patrick has just heard that the live show may be bumped for breaking news on the riots. Runner Kelly meanwhile, alongside her usual frantic eviction night tasks, is also juggling having to avoid calls from her long-term boyfriend Riq, who keeps ringing to find out exactly why she didn't come home last night. As tearful Scot Pippa is evicted from the house and interviewed by Davina, all hell is breaking loose outside. There's a complete massacre of the BB audience as zombies start to attack. Can Patrick and Kelly get to safety? And just what has happened to Davina?
After an encounter with a zombie, Riq meets lone armed survivor Alex. The pair team up and escape the zombies by hiding in an abandoned country house. BB Producer Patrick begins to realise that he is stuck in the green room with newly evicted Pippa and no communication to the outside world, no food and no way out – zombie Davina is patrolling the corridor outside. Grayson tries to nurse Angel whose health is rapidly deteriorating. Having found safety inside the BB house, Kelly, along with Marky and Space, now has to venture outside again. Armed with knives, the three speed off to the supermarket in the hope of getting the medication that could save Angel's life.
Kelly, Marky and Space make it to the supermarket. While Kelly and Marky gather supplies, Space waits outside and encounters two policemen who threaten to shoot him as a looter. Kelly and Marky are chased out of the supermarket by two zombies; the police shoot the zombies, but one of them gets bitten, and his colleague shoots him. He tells the others that those bitten die and turn quickly into zombies. Spotting a wound on Marky's arm and thinking it is a bite, the policeman goes to shoot him too; unable to reason with him, Kelly picks up the other policeman's gun and shoots him in the leg. More zombies appear, and Kelly, Marky and Space escape in the van. Meanwhile in the greenhouse Grayson tries to comfort Angel, but when she stops breathing Grayson realises he needs to kill her in case she turns into a zombie, but he hesitates and is attacked by the now zombified Angel who bites him fatally in the neck. Joplin and Veronica manage to force Angel into the pool, and stab Grayson in the head just as Kelly and Marky arrive. Seeing that Zombie Angel is unable to get out of the pool, they realise that the zombies are not intelligent. Kelly shoots Angel with the police officer's handgun and vows that they will win against them. At the country house Riq turns on the television, and discovers the E4 Big Brother live feed is still broadcasting. Alex hears a French broadcast on the radio and determines that a rescue boat across the channel has been established, but has no doubt left, stranding them and any other survivors. Suddenly, just as hope begins to fade, Riq is relieved to see Kelly and the others on screen.
With the waves of undead continuing their approach, Patrick and Pippa make a desperate bid for freedom, and Riq and Alex are placed in mortal danger. Meanwhile, Joplin forms a theory as to what caused the epidemic.
Riq and Kelly are reunited. Patrick is forced to be tied up when he wants to leave the house and leave the others in danger. Patrick tries to get Joplin on side as the housemates decide what to do with him. Joplin unties Patrick and he takes Kelly hostage and leaves the house with her and Joplin. Riq ends up getting shot and killed in a scuffle. Joplin opens the gates and the zombies make it into the Big Brother complex. Patrick is killed as he attempts to escape. Space becomes trapped in the Big Brother control room after trying to find Pippa but is bitten by a zombie. The zombies make it into the house and Kelly manages to make it into the diary room. Kelly decides to try and make her way to Space but fails.
