Tennison's investigation takes her to Bosnia with an old flame, a journalist with wide experience in the region.

Tennison's investigation takes her to Bosnia with her old flame, Robert West (Liam Cunningham), a journalist with wide experience in the region. There, she makes a crucial breakthrough. But on her return she is dismayed to learn that her prime suspect is in an international witness protection program. Inspired by her father's (Frank Finlay) reminiscence of liberating a World War II concentration camp, Tennison makes her move anyway, resulting in her dismissal from the case. Justice for the killer now hinges on the cooperation of the cop whose judgment Tennison spurned at the outset: DCI Finch.