A severed hand washes up on a Shetland beach, with further body parts discovered in a holdall that has been dumped at sea. Perez and the team begin a complex murder investigation.

Perez finds that the murder of the young Nigerian man is more than just the drugs trade but could be sex trafficking with the Shetlands a cog in a much larger wheel.

Hoping to find information on Paul Kieran, Jimmy goes to Glasgow. There, he and DI Sam Boyd from the trafficking unit pursue some leads. Plus, Jimmy can't visit Glasgow without seeing Cassie, which brings her to the attention of the people tailing Jimmy and puts her in danger, too.

Having heard of the traumatic events in Glasgow, an angry Duncan confronts Jimmy over his fears for Cassie's safety. Cassie, although shaken, seems pleased that Jimmy has trusted her with the truth. Grant, young plain clothes officer, is tasked with keeping an eye on her. Now sure that Zezi is still being held on Shetland, Jimmy and Sandy pay a visit to Morag Dunwoody in an attempt to get more information from her. Her attitude has changed completely from the day before, when she admitted to Sandy that Calum didn't transport the girls to the mainland. Morag is obviously shaken and Jimmy suspects that she's been warned off by the traffickers. That night, Morag's home is set on fire, but she escapes, terrified, with her young children and later admits that she received a phone call before the attack, from a woman with a Glaswegian accent. Andrea Doyle, the tattooist, becomes a potential suspect. Very affected by his kiss with Alice, Jimmy tries to meet up with her, but the investigation keeps getting in the way. When he finally does get the chance to see her, Alice admits that she's not sure how she feels about the situation and whether she still loves Chris or not. While Duncan is out for a drink, he sees Jimmy and Alice chatting intimately in a corner - but so does Chris. Sandy pulls an all-nighter going through CCTV and tracks down Andrea Doyle at a gas station near the Dunwoody's house prior to the attack. They manage to find an address for her and she is arrested after a chase. Frustrated by not getting any closer to finding Zezi and convinced that Jamie Hayes knows more than he's letting on, Olivia ambushes Jamie and Rosie, and drives off with Jamie in the car.

The discovery of Nikki's body intensifies the search for Zezi. Perez feels that time is running out. A desperate Olivia tries to get information from Jamie Hayes.

Perez closes in on Zezi's location at last. But can he reach her before it's too late?