Remorseful murderess Harriet Meagher
Harriet Meagher (Clare Cathcart) is the remorseful main villainess from New Tricks' eleventh and penultimate season finale, "The Queen's Speech" (airdate 20 October 2014). She is the best friend of Amy Taskerland, who was murdered on July 1, 1983.
It was uncovered that Amy had left a recorded message inside a capsule, where she expressed fear of someone named Alec. Under the belief that Alec was a boyfriend of Amy's, Gerry Standing and Steve McAndrew approached Heather regarding Alec, with Heather stating that while Amy had her share of boyfriends, no one named Alec was among them. Amy's headmaster, Nicholas Hines, was suspected after it was revealed that he was having an affair with Amy (who was 16) while he was engaged to fellow teacher Carla O'Brien, and the suspicion increased after Harriet stated that Hines was at the disco on the day of Amy's murder.
Further inspection of the tape revealed the true contents of Amy's recording: she was reciting The Queen's Speech--which was written to be read aloud in case of a nuclear attack, which England (among many other countries) was preparing for during that time. In addition, "Alec" was revealed as an acronym, standing for the Annihilation and Losses Estimation Committee, which had Amy's father, William Taskerland, was a member. Amy became distraught over William leaving her and his wife (Amy's mother), for his duties with the Committee, and as DCI Sasha Miller figured out, Amy's plan to confide in Hines fell through when she spotted him with Carla, leaving her with one person left to share her fears with: Harriet.
In the episode's climax, Sasha met with Harriet, and everything was revealed. On the night of the disco, Harriet comforted Amy when she told her about her father, ALEC, and the impending alerts regarding Armageddon (which died down). Harriet asked Amy to come with her, only for Amy to refuse and lash out at her and Harriet's parents, leading to a scuffle between the two friends. The physical confrontation ended with Harriet shoving Amy down the stairs and to her death, with Harriet expressing shock over accidentally killing her best friend before leaving the scene. During her confession, Harriet voiced her tearful regret and remorse over killing Amy, stating that while Amy was let down by her father, she let down her father (a priest) that night with her unintentional actions. Following her confession, Harriet was arrested (off-screen) by Sasha.