Redemption: Part 1 (S24E01)

When Jack and Nikki enter a high-security prison to investigate the suspicious death of an inmate, the case brings up disturbing memories for Nikki. The victim’s cellmate is Scott Weston, the student responsible for a mass shooting she witnessed ten years earlier. Nikki becomes increasingly convinced that Scott is their prime suspect, but Jack worries she is not following the evidence. (BBC iPlayer)