Faced with the prospect of travelling in second class Lady Felicia (Nancy Carroll) is delighted to run into opera legend Dame Bianca Norman (Cecilia Noble) who invites her and Mrs McCarthy (Sorcha Cusack) away from the riff-raff into her private pullman carriage.
Also on board is Bianca's fifth husband Piers Huntington (Matt Rawle) and adopted children Barbara (Olivia Hallinan) and Tony (Chris Lew Kum Hoi) who do not seem entirely happy with their life of luxury.
After midnight the train stops and the carriage is plunged into darkness, allowing local farmers Lenny (Darryl Clark) and Daryl Cudlip (Andrew Turner) to seize Bianca's jewels. In the scuffle Bianca is killed and the panicking brothers take Lady Felicia and Mrs McCarthy hostage.
Roused from their beds Father Brown (Mark Williams) and Bunty (Emer Kenny) visit the scene where Inspector Mallory (Jack Deam) promises to do all he can to find Lady Felicia and Mrs McCarthy. Meanwhile the ladies manage to break free at the farm, encountering younger brother Tim Cudlip (Jack Carroll) before an angry Lenny and Daryl return. With no clues as to where his friends are and killers on the loose, can Father Brown find them before it's too late