This season, Father Brown finds himself pitted against new Inspector Sullivan, as the priest attempts to solve cases more sinister than ever - an exorcism, an abduction, a poisoning and a murder put Father Brown's instincts to the test and his own livelihood at risk.

In this series the priest finds himself embroiled with the Secret Service, which puts Lady Felicia in a compromising position. Sid is sent undercover into a theological college to flush out a killer and Mrs McCarthy takes on a group of travellers when a local man is found dead. Finally a fugitive takes sanctuary in St Mary's. Father Brown is stunned to realise that the man in the confessional is in fact Inspector Sullivan - and he's wanted for murder.

This season, a man missing for years returns just as his wife is about to remarry, but when he’s found dead, suspicion falls on those closest to him. The village gets a dose of Hollywood glamour when a film crew arrives. And Sid’s romance with a brewer’s daughter gets complicated when he finds out she’s not only married and he is also her alibi for the night her father is murdered.