The Ghost Squad (2005)

The Ghost Squad stars Elaine Cassidy as Amy Harris, a young and idealistic undercover detective, whose work soon becomes a sinister and violent journey of discovery.
Recruited to the Ghost Squad by the tough Detective Superintendent Carol McKay (Emma Fielding), her new and powerful boss – they soon clash when Amy doesn't tow the party line. Amy's shadow and support in the Ghost Squad is Pete (Jonas Armstrong), a thrill-seeker with a dangerous edge. Depending on each other in the edgy world they inhabit, theirs is a relationship that is always electric.
Undercover for weeks or months on each case, the set ups are costly, and Amy can't afford to fail. But what is success? In the complex world of political expediency nothing is clear cut.