On the night of October 13, 2010, eyewitnesses called 999 when they discovered 18-year-old Niall Dorr lying unconscious on Castle Road in Dundalk, County Louth. He had severe head injuries and was later declared dead at Beaumont Hospital.

Newly-promoted detective inspector Pat Marry is put in charge of the investigation. It's his first case in Dundalk, and his team scour the town for clues, including CCTV footage and forensic evidence. An anonymous tip-off suggests Niall had been assaulted by a notorious local thug. But Pat faces a problem when terrified eyewitnesses refuse to make statements.

Pat is determined to deliver justice and provide closure to Niall's friends and family. So he turns instead to forensic science to catch the killer. He describes how he meticulously built the case, finally relying on a discarded cigarette butt and brand-new DNA techniques to identify Douglas Ward as the killer.

Niall's father Dave Dorr, along with his friends, talk about Niall, the circumstances of his death and the promising life that was tragically cut short.

In October 2018, a sleepy village in County Antrim is rocked when, in the dead of night, a gang arrives with a stolen digger and rips an ATM from the walls of the local newsagent.

Police are quickly at the scene, where they soon discover that the gang is highly skilled and has left minimal evidence. But this was only the first in a string of ATM heists by the gang, as they continued their work across the county.

As the attacks escalate, specialist detective superintendent Richard Thornton from the Organised Crime Division is appointed to lead the response, and assembles a dedicated team to tackle the sophisticated criminals.

Richard recalls how he and his team spent weeks meticulously analysing the gang's methods to predict their next move, and with the help of experts in surveillance, sought to put an end to the relentless attacks.

Chief superintendent Sue-Ann Steen provides insight into her leadership of the uniformed officers who patrolled the affected communities. Business owner Geoffery McKillop offers a personal account of the damage caused to his café during one of the gang's audacious attacks.

In Dublin in 1982, it was still illegal to be gay. But when Declan Flynn was brutally killed in a homophobic attack at a local park, the public was outraged.

Communities united in support of the gay community, beginning a decades-long process of social change. Over 40 years later, Declan's death is considered the catalyst of Ireland's Pride movement.

Retired detective inspector Edwin Handcock has never forgotten the case. He recalls every detail of the investigation, including the discovery of the sticks used to beat Declan to death. His inquiry led to the arrest of four men and a14-year-old boy. Their prosecution sparked further anger and controversy when they were handed suspended sentences for manslaughter.

The public took to the streets in protest, with a now-famous march across the city to the site where Declan died.

His siblings, Paul, Gabrielle and Lorraine, now speak emotionally on camera for the very first time about their brother's senseless killing. Local activists and national politicians also share the impact of this attack on their own lives as members of the gay community, and on Irish society as a whole.

In 2019 Pat McCormick, a 55-year-old father of four, is reported missing when he fails to come to work one morning.

When detectives speak to Pat's ex-wife and children, they get a picture of a loving and reliable father. So when he also fails to show up one morning to bring daughter Morgan to school, and no trace of him can be found, all are left gravely concerned.

Officers believe they're dealing with a missing persons case. But as they dig deeper, they uncover a call made by Pat to police on the night he disappeared.

It is clear from the call that Pat was concerned about his well-being and feared someone was out to get him. With this shocking information, the case is escalated to a possible kidnapping, and detective Heather Campbell is brought in to run the inquiry.

Heather and her team scan hours of CCTV to trace Pat's movements. They get their first break when footage shows him walking into the flat of his girlfriend, Lesley Ann Dodds, in Comber, County Down. However, he is never seen leaving.

Detectives also discover Lesley Ann is engaged to another man, David Gill, also captured on CCTV in Comber on the night of Pat's disappearance.

As a complicated love triangle emerges, this missing person case is declared a murder investigation, and the search for Pat's body begins. But detectives can find no sign of his remains.

If Detective Campbell is to put Pat's killers behind bars, she and her team must use everything at their disposal, from appeals to the public to cell site analysis and the use of specialist underwater search teams, to find the body. Colin Ferguson, search team leader, gives behind-the-scenes insights into his complex search operation.

Meanwhile, in a heartfelt account, Pat's daughter Morgan recounts the trauma she and her family endured while waiting for answers.

In the late 70s and early 80s, Ireland battles a growing heroin epidemic, leaving devastation in its wake. Stable, working-class communities collapse, becoming hotspots of addiction and crime.

At the heart of this turmoil is Larry Dunne, a petty criminal from Dublin's inner city, who has big ambitions. He rises to power, building a vast heroin trafficking empire and amassing incredible wealth as the city's streets descend into chaos.

Detective Michael O'Sullivan, who only recently joined the Irish police service, is tasked with being the first detective to go undercover in the fight against drug crime. Michael assumes the guise of an addict, infiltrating the violent underworld controlled by Dunne's network. He recounts the twists and turns of a high-stakes, four-year long game of cat and mouse to bring down Ireland's first heroin kingpin.

Anna Buckley is a local community journalist who describes how her community was ravaged by the drugs sold by Dunne's operation. Journalist and reporter Brendan O'Brien also shares how his work turned the issue into national outrage.

In 2013, a young Romanian woman approaches the Police Service of Northern Ireland (PSNI) about a gang that had forced her into prostitution.

Former detective chief inspector Dougie Grant and detective inspector Rachel Miskelly of the Serious Crime Branch are tasked with investigating this challenging case. Their first priority is to identify other victims to gather crucial evidence and help them escape exploitation. But inside the brothels, fear and grooming have silenced vulnerable women, making the task almost impossible.

With determination, Rachel and Dougie turn to digital forensics and piece together the movement of victims across international borders. They recall how, in a groundbreaking human trafficking investigation, the PSNI join forces with Swedish authorities, Europol and Romanian law enforcement to bring the leaders of this organised crime gang to justice.

In Stockholm, Detective Per Hjort and public prosecutor Eva Wintzell share unique insights into evidence gathering through covert surveillance and wiretaps. Through this, they're able to identify another victim and share intelligence to build a stronger case.

The most profound impact of this case is on the thirteen women who were rescued. Diane Hickey and Heather Woods from Women's Aid shed light on their efforts to collaborate closely with police and support victims throughout the investigation and legal process

In September 1992, Esther McCann and her 18-month-old daughter, Jessica, tragically lost their lives in a house fire in south Dublin.

What seems like a tragic accident takes a more sinister turn when retired sergeant Pat Treacy and superintendent Martin Walker uncover disturbing death threats leading up to the fire, all seemingly aimed at Frank McCann, Esther's husband and a respected swimming coach.

In one of the most harrowing cases of their career, Pat and Martin recall how as they dig deeper, Frank's claims of being targeted unravel, exposing a sinister web of lies that establish him as the central focus and prime suspect in the investigation. Crime scene mapper Michael Campbell details how the truth was uncovered in the ashes of the house fire, in a case that became one of the longest running trials in Irish history.

Esther McCann's niece, Esther Leonard, describes the effect these murders have had on her close-knit family and her fears for the future, if their murderer walks free.