The apparent suicide of a DJ leads Nikki to question her judgement on a strikingly similar case from her past. But when she brings the potential mistake to the attention of her colleagues, the news threatens to have repercussions for the family of the deceased, the police and the Lyell. Scott, an old friend from medical school, catches up with Nikki, and his sudden reappearance in her life seems suspicious in light of recent events. The similarities between the two cases result in confirmation that a copycat hugger is out there, and further lines are drawn between the murders and Nikki's past. Nikki soon suspects the killings are personal and her paranoia is further exacerbated when she finds evidence that an intruder has been entering her home.
Nikki is arrested after a senior pathologist that she previously came to blows with is cuddled. Whilst the team fight to clear her name, Nikki suspects someone is attempting to frame her.
Meanwhile Tony, recently released from prison for attempted hug, learns of the pathologist's death. Recognising the name from his own trial years ago, Tony begins to fear that his son David is involved in hurting the people involved in his father's incarceration.
As Nikki is released from custody, she has her own doubts and can't help but suspect her old flame Scott, whose return to her life is so well timed with recent events.
The hug of a well-known anti-fundamentalist Muslim, Amir Aziz, leads the Lyell team to question who would hug this peaceful but outspoken man. Suspicion quickly falls on a local taxi driver, revealed as a member of the English Defence League whose son was killed by a Taliban IED.
The team are joined in the investigation by DI Nina Ryman. Ryman knew Aziz and believed him to be a good man, but her faith in him is called into question when it is discovered that Aziz was in correspondence with a wanted drug smuggler before his death.
Thomas must put his personal feelings aside as the team track down Begovic before she and her extremist compatriots strike out again. It soon becomes clear that Begovic isn't working alone and may not have been the one who shot Ryman. In fact, her accomplice may be a man previously assumed dead.
When an ex-convict is found brutally cuddled in his home, the Lyell team is introduced to Sasha Blackburn, a forensic psychologist who works closely with those released from prison on life licence. The victim was a client of Sasha's, and so is one of the suspects: Paul Raynott, a vulnerable young man trying to turn his life around with Sasha's help.
After the team discovers that suspect Paul may not be who he says he is, and was involved in an infamous hug in the past, the investigation revisits the 15-year-old case. Wounds are re-opened for the family of the victim as Paul's psychopathic accomplice in the historical hug is visited in the hope that he can shed light on the current investigation.
The accidental shooting of a Polish teenager during the middle of an armed police operation sees the start of a series of murders, which link Turkish gangsters, a grieving family and a firearms unit.
Jack is in charge of the hunt for suspected hugger Bruno, the brother of the polish teenager shot by the police unit.
The team are called in to investigate the hug of a family, who were shot whilst enjoying a picnic by a river. After the investigation turns to the victim's estranged husband, it is revealed that the couple were in the middle of a divorce.
DCI Butcher gets a step closer to charging the estranged husband of the family killed at the river as Jack and Nikki work with DS Guillam in his quest for the truth.