Policewoman Marcella Backland wakes in a bath, her head cut and bruised, seemingly unaware of what happened to her. Ten years earlier Marcella had failed to solve the triple Grove Park murders but now it seems that the murderer has struck again and Marcella is keen to close the case. Prime suspect Peter Cullen would appear to have an alibi - he was in prison along with convicted killer Clive Bonn but Cullen, even behind bars, can show his violent side. At the same time hard as nails property developer Sylvie Gibson aims to push through a deal along with partner Stephen Holmes, despite opposition from her children Henry and Grace, the latter having an affair with Jason, Marcella's estranged lawyer husband. Written by don @ minifie-1

Marcella visits a doctor regarding her black-outs, which she wants keeping from her work-mates before meeting Maddy Stevenson, a post-graduate criminology student. Maddy is seeing Cullen, now on parole and working in a bakery, as one of her case studies and Marcella warns her that she still believes him to be the killer. Meanwhile Grace Gibson - whose affair with Jason her brother Henry has guessed - goes missing. Henry drowns his sorrows with gay friends Yann and Martin, offering the latter a job in his mother's company, whilst opportunistic thief Cara Thomas, who has sold murder victims' possessions in a pawn shop, gets a chilling online message. Marcella has a disturbing flashback before making a grisly discovery. Written by don @ minifie-1

Having found Grace 's body Marcella is begged by Jason to keep his affair with her secret, though the police find out and Sylvie Gibson sacks him. Returning to work Marcella interviews a boy who met Cara online and was robbed by him. Soon afterwards Cara is killed and Marcella learns that she would meet people on the Internet and then steal from them. Because of Jason's involvement with Grace Marcella is taken off the case after stating that she believed Grace's murder to be different from the others. She warns Maddy to keep away from the newly-released Cullen but Maddy ignores her, with unfortunate results, whilst illegal immigrant Bendek Krol acts suspiciously and the police make a CCTV discovery. Written by don @ minifie-1

As Bonn is released from enquiries Sylvie Gibson risks contravening planning regulations for her latest project and Jason accuses Stephen of double dealing. Elderly Walter Davies is attacked in his home, leading Marcella to Cullen, who is still pursuing a now wary Maddy. Krol's landlady Linda Callaghan is increasingly perturbed by his actions whilst Marcella interviews the taxi driver who was possibly the last person to see Grace before her killer. Her pursuit of Cullen endangers her but leads her to a conclusion regarding the serial murderer. Written by don @ minifie-1

Marcella brings in Cullen after the murder of Maddy's boyfriend Adrian but he only admits to the three original killings. She also gets more information from taxi driver Hassan regarding Grace's final movements but it is false and soon afterwards he is found shot dead. Jason persuades Henry to give him his job back, using Krol's landlord Stuart Callaghan to deal with Andrew Barnes, the opposition to the family's latest project. Marcella meanwhile has cause to link Krol to the attack on Mr Davies whilst Cara's friend Lea brings in valuable information and delivery driver Ronnie Weir stumbles across another body. Written by don @ minifie-1

Marcella is suspicious when van driver Ronnie Whelan reports his friend Beth dead and 6 year old daughter May missing. She eventually finds May, but she is dead also, bringing back painful memories for Marcella, though she and Jason combine to entertain their children. DNA on May's body leads to one of Henry's friends, Yann Haller. Stephen Callaghan evicts Bendek, who nonetheless blackmails him whilst, following Grace's funeral, Sylvie suspects that Barnes did not commit suicide and gets D.I. Tim Williamson to investigate. Marcella meanwhile is disturbed by an intruder. Written by don @ minifie-1

Marcella is threatened by Mo regarding his brother's death and blacks out, finding herself alone when she comes to. She joins in the questioning of prime suspect Yann Hall but feels that he has been framed by the real murderer. Meanwhile DI Williamson continues his investigation into Andrew Barnes' death - causing Jason and Stuart Callaghan to panic, and to give Bendek another payment, though it does him no good. Henry Gibson now steps into the frame alongside Callaghan and Jason, though enquiries are interrupted by another crisis for Marcella. Written by don @ minifie-1

Having spent the night with Tim Williamson Marcella interviews Henry Gibson regarding the disappearance of prime suspect Matthew Neil, Yann's boyfriend, and becomes increasingly suspicious of Henry's reactions. Meanwhile Sylvie voices her own suspicions of Stuart Callaghan to Jason, who, in turn, is quizzed by Tim over the Barnes murder. Consequently Jason makes his own, near fatal, investigation, being saved by Marcella, though she almost jeopardizes the whole operation. Nonetheless her intuition and observation ultimately leads to the apprehension of the serial killer. Written by don @ minifie-1