When Internet trolls start to drop dead, the Doctor thinks there might be more to it than just a sedentary lifestyle and high blood pressure. From the backstreets of South Korea to the jungles of Brazil, the Doctor and Donna follow the leads until they find the source of this online infection. But they aren't the only ones interested in these sudden deaths at the computer screens or what's causing them. Before long, Donna and the Doctor are fighting for their lives - and the lives of everyone else on planet Earth who uses the internet. In;lcuding some people very dear to Donna...