In 1928 Glasgow, Alan Finlay studies to become a qualified doctor, and dreams of becoming a surgeon. His landlord goes missing and Finlay follows a hunch which leads him to the town of Tannochbrae and a meeting which will change his life.
While in Glasgow to collect a leg brace for a young patient, Dr Finlay encounters a showman 'doctor' who later comes to Tannochbrae and treats the same patient with his 'scientific' methods, much to Dr Finlay's chagrin.
Dr Cameron's gardener Alex Dean (Patrick Troughton) is behaving strangely out of character. Is he certifiable, as Dr Snoddy believes or could Dr Finlay's more left-field diagnosis be correct?
Dr Finlay is called to a cave in at the local pit and back at Arden House, Dr Cameron is concerned when the insurance man takes an interest in housekeeper Janet.
When the local minister sees something strange at the house of Mrs Elgin, he asks Dr Cameron to investigate. Dr Finlay tries to help a local family with disastrous results.