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.

In England, the Pakistanis Yasmin lives two lives in two different worlds: in her community, she wears Muslin clothes, cooks for her father and brother and has the traditional behavior of a Muslin woman. Further, she has a non-consumed marriage with the illegal immigrant Faysal to facilitate the British stamp in his passport, and then divorce him. In her job, she changes her clothes and wears like a Westerner, is considered a standard employee and has a good Caucasian friend who likes her. After the September, 11th, the prejudice in her job and the treatment of common people makes her take side and change her life.