A room full of gold is infected with a new sort of virus that quite literally eats gold. It is up to Ros to make an antidote to return the gold to normal, and she doesn't have long- after some time, and once the gold has reached a certain temperature, it will be irreversible and the gold will be lost forever. Ed is trapped in the room with the gold and also two security things that continuously try to shoot him. Beckett decides to get Ed out of the room, as the antidote Ros creates is harmful to humans, but his only way to get to it is by going through a tunnel filled with toxic fumes. (thetvdb.com)