Sylvester McCoy has given fans some early details about his Father Brown character, who just so happens to be another doctor.
The beloved actor, who turned 80 last summer, is still remembered fondly for his performance as the Seventh Doctor in Doctor Who, with his latest role being a more typical medical practitioner (as opposed to a Time Lord).
"He’s a retired doctor," McCoy said of Angus McClurgy, his character in tomorrow's episode of Father Brown.
"Nowadays, I get offered retired doctors and weird characters. They say, 'We need a retired, weird doctor character – I know who can play that part!'"
Dr McClurgy is the titular Hermit of Hazelnut Cottage, who once housed Brenda Palmer (Ruby-May Martinwood) as an evacuee during the frightening days of the Second World War.
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In the years since they parted ways, he has increasingly "turned in on himself", which certainly isn't helped by plans to redevelop the village he calls home.
McCoy explained: "They want to knock down his house. He doesn't want that to happen, because it's his house and contains his memories of his past and his loves and his losses and all that. So there's that battle going on with the developers.
"He is very grumpy and bad-tempered, and threatens to kill someone. And so, obviously, he becomes the number one suspect for a while, until number two comes along, then three and four."
Fans will have to tune in to find out whether Dr McClurgy is indeed the culprit, but McCoy hopes that viewers will take more away from the episode than a simple murder mystery.
He added: "The story about the doctor’s friendship with Brenda is a kind of platonic love story between two people of different ages. There are many other stories entwined in this episode, as well.
"But, for my part, that will be one of the things that people take away: how grumpy old people can be saved by caring young people."
In addition to McCoy and Martinwood, this week's Father Brown stars Mark Williams in the title role alongside Melanie Walters as Dotty, Claudie Blakley as Mrs Devine, Tom Chambers as Chief Inspector Sullivan and John Burton as Sergeant Goodfellow.
Father Brown airs on Fridays at 1:45 on BBC One and BBC iPlayer. All episodes from this series are available to watch on BBC iPlayer now.