In The Theatre Of The Invisible written by David Semple, Father Brown (Mark Williams) accompanies Mrs McCarthy (Sorcha Cusack) to a heat for the BBC radio quiz Up To You in the village hall.
Producer Jeremy ushers them through, where Richie (Arthur Bostrom) is the announcer, Joyce (Jessica Turner) sings the theme tune and Barney (John Henshaw) is the ebullient quizmaster. Curmudgeonly landlady Mrs Rudge (Lynda Baron) is unfairly eliminated while Bunty (Emer Kenny) and Mrs McCarthy sail though to go head to head on the live show next week.
Afterwards at her boarding house, Mrs Rudge is vile to the BBC cast and reveals she’s even read Richie’s salacious diary. Later when Jeremy returns with Bunty they’re shocked to find the guesthouse on fire.
As Mrs Rudge’s corpse is removed, Inspector Mallory (Jack Deam) pronounces it an accident but when Father Brown looks closer he finds a device in the chimney designed to block it. Mrs Rudge was murdered…
Father Brown: The Theatre of the Invisible airs on Tuesday 10 January 2017 from 1.45pm-2.30pm on BBC One