Pc Beth Green arrives at the scene of a suspected suicide at a motorway bridge, and is horrified to find the deceased is Lucy Burton, the young runaway she had bonded with. In the mortuary, forensic investigator Eddie Olosunje tells DS Stuart Turner and DC Terry Perkins that this was not suicide – Lucy was murdered.

Beth goes to Lucy’s house to talk to her housemates Kim Law and Sarah Fuller, and when Lucy’s boyfriend, Mark Lawrence, leaves for work, Beth uncovers some video tapes that reveal he was having sex with Sarah, Kim and another girl, Ellie Rogers. Later, Mark’s car is found on fire in an attempt to destroy DNA evidence.

Delving into Mark’s past, Terry discovers that Mark was fostered by Doreen Hutton, who reveals she was forced to evict Mark when he was 16 because he had a hold over twin girls she was also looking after. Doreen explains that both girls tried to commit suicide when Mark stopped calling, but one survived – Ellie Rogers.

Stuart and Terry find Ellie with Mark, who is arrested and brought in for questioning. Will Mark tell the truth about Lucy?

VIDEO: Watch a clip from this episode of The Bill.