Obviously, obviously Marcella should not have been welcomed back to work after the events of season one. That’s a given.  Investigating your husband’s mistress’ murder while being unable to rule out the possibility that it was you who’d killed her? Not optimum police work. Using insider access to destroy CCTV evidence showing that, in a fugue state, you’d taken said mistress’ corpse from the murder scene and buried it in the woods? Somebody fire this cop.  Add to that finding the real killer (10 points!) but then almost suffocating him to death in another fugue state (-1000 points), and still the HR Department at Edgware Road Police Station didn’t suggest early retirement for DS Backland. Back she came for season two, very much the ‘hold my beer’ season of crazy pulp crime TV.  Not literally though – the leap off the police station roof teased from the season’s opening minutes didn’t happen. Rav gently talked Marcella down from the ledge, and was repaid for his kindness by being knocked unconscious and handcuffed to the precinct toilets while she disguised her identity by cutting her hair and face, and made good her escape. After that, Marcella lived rough for nine days before being recruited into a shadowy undercover police unit after inadvertently faking her own death. In series one, Marcella had paid a homeless woman for a DNA cheek swab to substitute for her own. (Which she couldn’t submit to the investigation without it being discovered that she’d been present at Grace Gibson’s murder scene). By great coincidence, that homeless woman was killed in a fire on the very day that Marcella gave ex-husband Jason sole custody of the kids and dropped out of the real world. The bodies were so badly burned only DNA identification was possible, thereby Marcella was declared legally dead. 

‘Kill one to save many’, Jane Colletti’s serial murders, Joel Lawrence, Leo Priestley and Edward Backland 

Before the Juliette revelation, Marcella very nearly lost her son Edward to season two’s crazed serial killer. Jane Colletti was the mother of one of Edward’s schoolfriends and was revealed in the season’s penultimate episode to have abducted and murdered 17 children over several years. Jane used her medical skills as a midwife to sedate her victims and insert wooden tokens decorated with protective symbols into their abdomens, before lobotomising (and thereby killing) them. She would then surround their bodies with toys and bury them in symbolic locations around London where she felt that innocence had been abused.  Jane’s first victim was her brother Joel Lawrence, the paralysed patient being treated by Gail Donovan in a care home. Joel was thought to have been injured in a car collision in Norway. In fact, Jane had caused his injuries in order to – as she saw it – stop a cycle of incestuous sexual abuse by locking the ‘evil’ inside Joel. Their father had abused them as children, and after his death, Joel tried to abuse her.  That started Jane on a series of murders, all of them an attempt to stop children – many of whom had suffered abuse – from becoming abusers themselves. She drugged and abducted Marcella’s son Edward, thinking him a future abuser. She abducted and killed nine-year-old Leo, a school friend of her daughter and Edward, after hearing that he planned to hurt the girls at their school. As well as keeping the secret of Debbie Canavan’s death, Reg and his band manager Alan were also secretly former lovers. When Reg, suffering from incurable pancreatic cancer, threatened to come clean about everything, Alan kissed him and then off-screen drowned him in a London canal.  Jane had buried another child under the lift shaft at Edgware Police Station because that’s where her brother had gone to report their father’s sexual abuse, but had not been believed.

Paedophile Phil Dawkins, KidsCall and abductee Adam 

When Leo’s corpse was discovered in the wall of Reg’s former flat, Marcella suspected convicted paedophile Phil Dawkins of the murder. The stress and press attention led to – Phil thought – his girlfriend’s miscarriage, so to get revenge on Marcella for his child’s death, he held her son Edward hostage and threatened to rape him. Because Marcella’s colleague Mark was spying on her through her laptop’s webcam though, he saw Phil with Edward in her home and gave the police an anonymous call, stopping the attack.  KidsCall was how Jane groomed her latest victim, Adam, a young boy living in fear of his sexually abusive father. Adam managed to escape from captivity at the abandoned farmhouse where Jane was keeping him, and enlisted the help of two passers-by. When Jane discovered him missing, she killed a truck driver, stole his truck and used it to shunt the car containing Adam and his rescuers into the path of an oncoming train, killing them both and putting Adam in a coma. Maya’s husband Vince was a suspect in the murders due to his connections to one missing victim, whom he’d mentored at a local boxing club. After he was seen with another suspected victim, Vince was blackmailed by Eric Donavan, a disgruntled former employee. The boy in question though, turned up unharmed, the whole thing having been set up by Eric to get money from Vince. Vince’s blackmailer was the brother of Gail Donavan, the care worker who’d been communicating with Jane’s paralysed brother Joel Lawrence during her shifts. To stop her from learning the truth about his injuries, off-screen, Jane abducted Gail and killed her, sinking her body in the Thames.  Jane also killed Rosio, the girlfriend of a neighbour at the murder farmhouse where she was keeping Adam captive. Jane had abducted her to keep the neighbour quiet, instructing him via a chat room to frame Vince Whitman for the murders. When the neighbour learned that Rosio was dead, he shot dead Marcella’s colleague Mark and then himself. 

Marcella vs Jane: ‘You’re f***ing with the wrong mother’

Before signing over custody of her kids to Jason, who planned to take them to live with him and new partner Becky in Singapore, Marcella brought down Jane. In a fugue state, realising that Jane had taken Edward, Marcella abducted Jane’s daughter in turn and traced her to a wine warehouse where she was preparing to kill Edward. Marcella held Jane’s daughter at knifepoint, then wrestled Jane to the ground and brought her in for a full confession.