PBS | 9:00 pm
Leonard (Al Weaver) becomes pivotal to an investigation as he’s a witness to, and a victim of, a post-office robbery in the new "Part Four" of the series’ third season. Complicating the probe is the fact that the prime suspect is dead, but Sidney (James Norton) believes someone else with inside information is the culprit. Geordie (Robson Green) gets a very personal shock from Margaret (Seline Hizli). Morven Christie also stars.