Natalie Buxton wastes no time in visiting Emira and is intrigued to learn that she is a chemistry student. Before long, she has bulled Emira into constructing a secret mini laboratory to concoct crystal meth. But the plan backfires when the two Julies discover Emira spooning a mysterious potion out of her kettle and jump to the conclusion that she's making ricin. The rumour is fuelled when a sudden illness strikes down the inmates. Could it be poison? The signs seem there, particularly when Bev and Tina collapse for no reason, and worse is to come when Natalie's violent sidekick, Ashlee, and Wing Governor, Neil Grayling are found dead.

As the Emergency Services are called in to deal with the epidemic, Lou struggles to keep control on G-Wing. All of the inmates and the POs are panicking. Hollamby has had enough - she's not hanging around to get poisoned - and leads the other POs in a walk out. The inmates decide to do the same, and after locking Donny into the four-bed dorm and stealing his keys, they make a break for it. They get as far as the gates where they are surrounded by the police and held back at gunpoint.

Lou goes to confront Emira and is shocked when the inmate reveals that she's pregnant. It is now clear that there must be another culprit. With G-Wing practically deserted, Lou is pleasantly surprised when usually rebellious inmate, Pat Kerrigan, steps in to show her support. She and Emira help new SMO, Rowan Dunlop to care for a dangerously ill Tina. Rowan has his hands full with the epidemic and calls in the Health Protection Unit to help him quarantine the prison. They are running blood tests in an attempt to discover the cause of the outbreak, but the women are dropping like flies and time is running out.

Lou and Rowan work out that Neil was the first victim of the mystery virus, and when a leaky air-conditioning unit is found in his office, Rowan realises that the prison has been struck down with Legionnaires' disease. He radios his discover to the police officers guarding the front gate, but the walkie talkie he's using is defective. By the gate, the inmates are getting restless, none more so than Phyl. She's sure Bev will die without immediate medical attention, which leaves only one option. As the riot police move in, Phyl picks up Donny’s discarded keys and leads Bev on a dash down the corridor leading to the side entrance. Phyl opens the gate and makes a run for it, but is shot by an armed police officer.