The team assists DI Paul Renick following the assumed suicide of Jamal Al Sham and discover that he was murdered and was a people smuggler, blamed by Varkey Khoury, head of a family of Syrian refugees, for killing his wife. Varkey's 15 year old daughter Akka approaches Nikki for news of her mother, leading to Nikki sheltering her whilst the police haul in another young woman Tamara as a likely killer. At the refuge camp in Calais apparent altruist Yusuf Hamed assists 12 year old Sosa to come to England whilst Kalil Aziz, an associate of Sham, is also murdered and the police and pathologists make a grim discovery in an English forest.

The pathologists join the police in removing the corpses of the refugees who suffocated in the locked van and find a possible clue in phone messages sent by the dying victims. Whilst a customs officer due for retirement is suspected of allowing the people smuggling the team establish that the culprit took money from the relatives of the migrants he then left to die, Akka's mother among them. Yusuf rescues another batch of refugees from a second locked van, escaping with Sosa before the police arrive but the real clue surfaces via a Syrian charity to which the killer donated the victims' monies.