Plot

Father Brown struggles to save Sid from himself when he vows vengeance on his former defence barrister.

Lady Felicia's former chauffeur Sid Carter is released from prison, swearing vengeance on Giles Foster, his defending barrister whom he believes deliberately suppressed evidence, so that he is the prime suspect when Foster is murdered. Father Brown is convinced the alleged victim was bribed to protect the real culprit and his suspicions are increased when a hitman tries to kill him. Now the father has two objectives - to catch the actual murderer and stop Sid from getting to them first.

Sid Carter is released early from prison for good behavior during a year conviction for assault on Judith Miles, then a prostitute, now working in a solicitors office, which he still denies. Bent on revenge, Sid confronts his defense lawyer Giles Foster, at the party, attended by Brown, for his promotion to judge at the home of a Edward Reese, who chairs the committee. Foster is fatally stabbed in the throat with a piece of the champagne glass smashed by Sid, who is arrested, accused by Reese's wayward son Randolph. Father Brown becomes a target of a paid assassin and finds the only clue Sid held, an affidavit, burnt to ashes, so he must work on the last possible witness and set daring traps to expose the surprising murderer.—KGF Vissers