Professor Ambrose returns as the celebrated university scholar. However his mind is not what it once was as he gets increasingly forgetful.
This is a more sombre episode. It starts off with a flashback as someone is killed by a mysterious beaked person.
Professor Ambrose has come across an old diary. A secret chamber when the university was constructed over 300 years ago that might contain the mysteries of making gold or some other treasures.
What Father Brown finds is a dead body of a student who may had come in possession of a medal that could lead to further clues. The forgetful Professor Ambrose is accused of his murder and Father Brown must come to his rescue.
Father Brown gets to be Indiana Jones in this episode. Sunlight pointing the way to hidden rooms. Maps about a village that suddenly disappeared. A box that should remain unopened.
An intriguing episode but one I felt where the villain was signposted. Sometimes the casting can be a big pointer and the episode needed a few more red herrings.