When a man plummets from a high-rise building, the Lyell team cross paths with the NCA and a notorious mafia group, pushing Nikki to make a tough decision.

Nikki becomes even more involved with the Ndrangheta mafia-group and Jack uncovers some disturbing leads. An unlikely alliance leads Nikki closer to the truth, but not without some collateral damage.

A lorry is found with people locked inside, some dead. With the survivors refusing to speak, Nikki and the team must use their pathological and forensic skills to identify them.

The Lyell team work together to find out why the lorry was found with bodies inside and a dead driver at the wheel, and are truly shocked to discover where it leads them. Gabriel becomes emotionally invested and is presented with an ethical dilemma, and Jack gets a surprise visit.

The Lyell team are thrown into the dark side of social media, where nothing is as it seems, and the perfect profiles of the influencers they are investigating raise disturbing questions. As a heavily pregnant DI asks the team for their expertise, are they running out of time to solve this case?

The investigation continues to take unexpected turns, with Nikki managing to get behind the mask of the lead suspect. Jack has a breakthrough at the festival site and Nikki takes a dangerous opportunity. A surprise event at the Lyell brings some hope.

Levelling-up leaders and environmental activists clash in a small town trying to look to the future. With a sabotaged train and a dead mayor, the activists become suspects.

The Lyell team return to the crime scene as another victim is in peril. Family ties are tested to their limits as they reveal the dark secrets that led to the tunnel collapse, and Jack is put in a difficult position when a blast from the past comes to visit.

Jack is sucked into a complex case where he's pitted against his former mentor. The tight-knit group of police officers provide a difficult case where nothing is as it seems.

As the evidence mounts against the accused police officer, the local CID finds dissent within their ranks. The Lyell team unveil corruption and deceit within the local jurisdiction, with deadly and wide-reaching consequences.