Christmas day, and DCI Tom Reynolds receives an alarming call. A mass grave has been discovered on Oileán na Caillte, the island which housed the controversial psychiatric institution St. Christina's. The hospital has been closed for decades, and onsite graves were tragically common. Reynolds thinks his adversarial boss is handing him a cold case to sideline him. But then it transpires another body has been discovered amongst the dead - one of the doctors who went missing from the hospital in mysterious circumstances 40 years ago.

Late one night a man walks into the luxurious home of disgraced banker Harry McNamara and his wife, Julie. The man launches an unspeakably brutal attack on Harry as a horror-struck Julie watches, frozen by fear. Just an hour later the attacker, JP Carney, has handed himself in to the police. He confesses to beating Harry to death, but JP claims that the assault was not premeditated and that he didn't know the identity of his victim.

When young London professional Alex Evans is informed that his sister's body has been pulled from an icy lake in Northern Lapland, he assumes his irresponsible sister accidentally drowned. He travels to the wealthy winter resort where Vicky worked as a tour guide and meets Agatha Koskinen, the detective in charge. Agatha is a no-nonsense single mother of three who already thinks there's more to Vicky's case than meets the eye. As the two form an unlikely alliance, Alex also begins to suspect the small town where his sister lived and died is harbouring secrets. 

It's June 2008 and 21-year-old Adam Lattimer vanishes, presumed dead. The strain of his disappearance breaks his already fragile family. Ten years later, with his mother deceased and siblings scattered across the globe, Adam turns up unannounced at the family home. His siblings return reluctantly to Spanish Cove, but Adam's reappearance poses more questions than answers. The past is a tangled web of deceit. And, as tension builds, it's apparent somebody has planned murderous revenge for the events of 10 years ago.

Five years ago, Erin Kennedy moved to New York following a family tragedy. She now lives happily with her detective husband in the scenic seaside town of Newport, Long Island. When Erin answers the door to Danny's police colleagues one morning, it's the start of an ordinary day. But behind her, Danny walks to the window of their 4th-floor apartment and jumps to his death.

On Doogort East Bog, Achill Island, a body is found. The close community is stunned to learn that it's Lisa Moran, a popular teacher who disappeared two days earlier. DS Lucy Golden is assigned to the case. For her, it's personal. As an Achill native, she knows that sometimes great evil can lurk in plain sight. Having moved back from Dublin, she has spent the last 10 years trying to prove herself to her colleagues after her husband was jailed for fraud. This is her chance to put the past behind her.

On his first week on the job, Garda Cormac Reilly responds to a call at a decrepit country house to find two silent, neglected children waiting for him - 15-year-old Maude and five-year-old Jack. Their mother lies dead upstairs. Twenty years later, Cormac has left his high-flying career as a detective in Dublin and returned to Galway. As he struggles to navigate the politics of a new police station, Maude and Jack return to haunt him. What ties a recent suicide to the woman's death so long ago? And who among his new colleagues can Cormac really trust?

Cathy Connolly discovers the bones of a baby concealed in the hem of an old wedding dress. When the dress' original owner, Lavinia Grant, is found dead in a Dublin suburb, Cathy is drawn deep into a complex web of secrets and lies spun by three generations of women. Meanwhile, a fugitive killer has already left two dead in execution style killings across the Atlantic - and now he's in Dublin with old scores to settle. Can the team track him down before he kills again?

Was the biggest case of his career the worst mistake he ever made? Ten years ago, DCI Jack Logan stopped the serial child-killer dubbed "Mister Whisper", earning himself a commendation, a drinking problem, and a broken marriage in the process...When another child disappears a hundred miles north in the Highlands, Jack is sent to lead the investigation and bring the boy home. But as similarities between the two cases grow, could it be that Jack caught the wrong man all those years ago?

Detective Chief Inspector Ryan retreats to Holy Island seeking sanctuary when he is forced to take sabbatical leave from his duties as a homicide detective. A few days before Christmas, his peace is shattered, and he is thrust back into the murky world of murder when a young woman is found dead amongst the ancient ruins of the nearby priory. When former local girl Dr. Anna Taylor arrives back on the island as a police consultant, old memories swim to the surface, making her confront her difficult past.

Former soldier. Ex-copper. Current man on the edge. Shunned by his old colleagues, and dividing his time between a dead-end job and the bottom of a whisky bottle, former Police Scotland detective superintendent Bob Hoon’s life is a mess. Then an old face from Hoon’s Special Forces days turns up asking for help: His teenage daughter has been missing for months, the police have drawn a blank, and he needs the kind of help that only Hoon can provide. And besides, Hoon owes him one.

On a leafy suburban street in Dublin, beautiful, poised Stella Greene lives with her successful husband, Matt. They're the perfect couple in every way, and Stella appears to have it all. Next door, at number 72, however, lives Rea Brady. Gruff, bad tempered and rarely seen besides the twitching of her net curtains, rumour has it she's lost it all...including her marbles, if you believe the neighbourhood gossip. But appearances can be deceiving, and when Stella and Rea's worlds collide they realise they have much in common.

They think I’m an idealistic young law student, that I’m passionate about reforming a corrupt and brutal system. They think I’m working hard to impress them. They think I’m here to save an innocent man on death row. They're wrong. I’m going to bury him.

2017: 19-year-old Tallulah is going out on a date, leaving her baby with her mother, Kim. Kim watches her daughter leave and, as late evening turns into night, which turns into early morning, she waits for her return. And waits. The next morning, Kim phones Tallulah's friends, who tell her that Tallulah was last seen heading to a party at a house in the nearby woods called Dark Place. 

A young woman is brutally attacked on her way home. It looks like she was the victim of a jilted—and twisted—ex-lover. But then two more women, also engaged to be married, are found dead. The press call the killer the "Surrey Stalker". And there’s a stack of similar cold case files. The pressure is on for young, ambitious DI Rob Miller. But with all the time he’s spending at the office, Rob’s also running a fine line trying to keep his fiancée, Yvette, onside as they try to plan their wedding.