A gang of tough London gangsters get more than they bargained for when a group of businessmen make an offer to buy their club, the Inferno. They turn out to be nothing less than Vampires wanting their land back and turn viciously on the gangsters when their demands are not met.

Tense drama series about the different challenges faced by the British Security Service as they work against the clock to safeguard the nation. The title is a popular colloquialism for spies, and the series follows the work of a group of MI5 officers based at the service's Thames House headquarters, in a highly secure suite of offices known as The Grid.