The series tells the fictional story of Alex Drake (played by Keeley Hawes), a policewoman in service with the London Metropolitan Police, who is shot in 2008, and inexplicably regains consciousness in 1981.
The first episode of the series reveals that, in the present day, Drake has been studying records of the events seen in Life on Mars, in particular Sam Tyler. Upon waking in the past she is surprised to meet the returning characters of Gene Hunt (Philip Glenister), Ray Carling (Dean Andrews) and Chris Skelton (Marshall Lancaster) all of whom she has learned of from her research, the trio having transferred from the Manchester setting of Life on Mars (Manchester and Salford Police) to London.
Tension between Drake and Hunt is built through the unsatisfactory explanation of Sam Tyler's absence, and the perceived underhandedness and shoddy work of Hunt in contrast to the methodical, ethical and thoroughly modern Drake. Continuing the theme of Life on Mars, throughout the series it is ambiguous to both Drake and the audience whether the character is dead or alive in the present day and to what extent her actions have any effect on events.