Charlie gives Dawn a bottle of perfume, unaware it contains more of the toxin. She collapses and is rushed to hospital within minutes of spraying herself with it. Nick is keen to get back to work but is still struggling with the trauma he went through, while Tracy's faith that the worst had passed is shattered as the team races to discover what else has been missed.

As the city struggles to cope with the renewed panic, Tracy learns that the contamination radius might be even bigger than last time. The second poisoning outbreak is much worse than the first, the random discovery means the poison could be anywhere.