Played by Keeley Hawes ("Mutual Friends"; "Tipping the Velvet"), Alex is originally from 2008, where she lives with her daughter Molly and has regular contact with her godfather Evan White. She travles back to 1981 after she is shot in the head when a hostage situation goes horribly awry.
She wakes up to find herself face to face with DC Chris Skelton, DS Ray Carling and the fabled DCI Gene Hunt - the characters from "Life on Mars" - as well as a new addition to the team - Shaz Granger.
Alex initially believes that everyone around her is an imaginary construct her dying mind has created having assimilated Sam Tylers fantasies. She spends the first series attempting to save her parents - two very well known lawyers who were killed in a car bomb in front of Alex's own eyes when she was a child - believing that this will be her key to getting home to her daughter.
However, all her beliefs are confused during the second series - particularly with the arrival of Martin Summers who is also from 2008. The series 2 finale further confuses things when Alex awakes in 2008, only to be plagued by images to Gene telling her to "wake up".
Throughout the programme, Alex has also begun to accept the others as more than her imaginary constructs, and becomes quite close to them. In S02E07...