 This episode revolves around a cold case from May 1945, where a young girl was found stabbed to death in a London back street. The identity of the girl is finally revealed by her diary which was found in a derelict house. DC Mel Silver seemed to have worked on the case just before her death. So says Sarah, a Nazi hunter, who pretends to be working for Interpol. She sent a ceremonial SS-dagger to Boyd s team; this turns out to be the murder weapon, and it came from that same house, belonging to a family of Jewish-Polish decent, who seem to have a lot of secrets, leading right back right to the darkest chapter of German history. Meanwhile people start dying in the "now". To tell much more would be a spoiler. Expect a starring performance by Eileen Atkins as the matriarch.