Scarred by the troubles in Belfast, Billy Nelson returns to his loyalist roots following his discharge from army service. But an outbreak of gang violence forces Billy to move on to Edinburgh, where he muscles in on the capital's drug trade. As the balance of power tips, underworld rivalries between Edinburgh, Glasgow and Belfast spill onto the streets. With a spate of horrific incidents and a trail of victims, the pressure is mounting for Grace Macallan, new superintendent of the Crime & Counter Terrorism Directorate.

Grace Macallan is at breaking point, and a new investigation is testing her to the limit. An undercover officer is missing and a woman is washed up, traumatised and barely alive, on the shores of Berwickshire. As she untangles the woman's story, Grace is drawn into a cold-blooded criminal world headed by Pete Handyside, a notorious gangland boss who will fight hard and dirty to control his empire. But a traitor in his midst is intent upon betrayal, triggering an uncontrollable wave of violence. As she hones in on crucial evidence, Grace knows that one wrong move could end in tragedy. 

A nine-to-five job away from the frontline isn't all it's cracked up to be for Grace Macallan. So when she's sent to investigate a suicide at Glasgow's notorious Barlinnie prison, Grace gladly escapes her desk. The dead inmate is Tommy McMartin, heir to a ferocious criminal family - though his murder conviction for killing his gay lover saw him cast out. The investigation drags Grace into contact with old McMartin adversaries - but the dynasty is under threat, and as it topples, buried secrets are unearthed.

At Police Scotland HQ, Grace Macallan has pitched up in Counter Corruption. But the demons of her past are never far behind. Meanwhile, Edinburgh's gangland is in turmoil, with territory battles causing serious havoc. Into the war steps DI Janet Hadden. An ambitious risk-taker, she knows how to throw opponents off balance. When she's thwarted, Hadden seeks help from a notorious underworld fixer - only for Grace to start an investigation that threatens to uncover all Hadden's secrets. 

Iceland, 2017: When a young Italian tourist is found brutally murdered at a sacred church in northern Iceland, Magnus Jonson, newly returned to the Reykjavík police force, is called in to investigate. At the scene, he finds a stunned TV crew, there to film a documentary on the life of the legendary Viking Gudrid the Wanderer. Magnus quickly begins to suspect that there may be more links to the murdered woman than anyone in the film crew will acknowledge.

Arthur Meadows has just returned home in his HGV from a long trip to southwest Europe, supposedly bringing back a consignment of cloth, yet is actually bringing back something far more deadly. Meanwhile, a young Asian couple are murdered in their small house in the middle of Gloucester, the killings done with ruthless efficiency. Beverley Wharton, now Chief Inspector, does not relish the investigation of the murders because she does not get on with her new sergeant, and because the pathologist Charles Sydenham would not have been her first choice.

When Mark Hartmann is asked to perform a post-mortem on a lab assistant killed by cancer, everything looks straightforward. But his initial findings are surprising: Millicent Sweet appears to have died of several different, aggressive tumours. Before he can discuss this with colleagues, he's called to a conference in Scotland. A serious error of judgement gives a pharmaceutical company a handle on him, and they threaten to expose his excesses unless he falsifies his report on Sweet.

St Benjamin's Medical School is the greatest of its kind, any death occurring within its walls would have created ripples within the academic world, but the death of Nikki Exner is far from being ordinary. Raped, and then grotesquely executed, her theatrical murder horrifies everyone. John Eisenmenger, a former forensic pathologist, finds himself dragged unwillingly into the case. Teaming up with solicitor Helena Flemming, Eisenmenger sets out to discover what really did happen to Nikki Exner.

It is the stroke of midnight on Hogmanay when Alison Reid admits a caller to her home. When her death is later reported, DI Clare Mackay attends the scene. The initial evidence does not rule out murder, but it’s not possible to say for certain if foul play was involved. Yet when the pathologist informs Clare about a post mortem of a young woman found in the Kinness Burn, and with some similarities to Alison’s case, it seems there’s a strong chance that there’s a killer on the loose in St Andrews.

A Cologne detective asks Jan Fabel for his help in tracking down the Carnival Cannibal, a terrifying serial killer who kills at the start of the world-famous annual Carnival. Unknown to anyone, Fabel's deputy, Maria Klee, also heads for Cologne to hunt down a different, even more dangerous killer - one with whom she has a score to settle. Taras Buslenko, a Ukrainian special-forces commander, prepares his undercover unit for a "black" operation into Cologne.

Eisenmenger has reluctantly taken a job as a locum in the pathology department of St Christopher's Hospital - his partner Helena is pregnant and they must prepare financially for the baby's arrival. John doesn't relish the prospect of being back on the treadmill, working within the NHS again, but when he is unwilling to accept his boss' "death from natural causes" diagnosis after autopsies on various bodies, his professional suspicions are piqued.

In the far north of Norway a man lives a peaceful existence. However one day his younger brother, always the more successful and charming of the two, turns up to visit, accompanied by his new wife. It soon turns out that the little brother is not quite as angelic as he seems.

Alastair Cunningham wakes up in hospital with almost total amnesia. But he knows that something terrible happened in his past, something that haunts him still. A young family friend, Clemence, is called in to help rekindle his memory. Retreating with Alastair to his remote cottage, Clemence finds a peculiar manuscript hidden away from prying eyes. Reading the prologue, she discovers a murder by someone very much like a young Alastair. The victim? Clemence's grandmother, Sophie.

When policewoman Eva Perry goes deep undercover to help bring a vicious local crime ring to justice, both she and her boss - Chief Detective Inspector Beverley Wharton - know there are huge risks involved. A series of unexplained and bizarre suicides forces Beverley into close contact with her former lover, the renegade forensic pathologist John Eisenmenger, who is already investigating the sudden suicide of his colleague Daisy Pemberton.

Six years ago, Evie Cormac was found hiding in a secret room in the aftermath of a brutal murder. But nobody has ever discovered her real name or where she came from, because everybody who tries ends up dead. Forensic Psychologist Cyrus Haven believes the truth will set Evie free. Ignoring her warnings, he begins to dig into her past, only to disturb a hornet's nest of corrupt and powerful people who have been waiting to find Evie - the final witness to their crimes. Unbeknownst to him, Cyrus is leading them straight to Evie. The truth will not set her free. It will get them killed.