The story is set in Yorkshire, in a fictional village in the middle of nowhere called Clarford. The doctor there makes his living off of the ailing Lord Clarford, and is very well educated. When he's not caring for the Lord, he's mending hurts down in the village.
How would he deal with a case of amnesia? What did they know about amnesia at the time? Is there any way that he could figure out the patient is pretending to have amnesia, other than making the person slip up and mention some detail of their past they're supposed to have forgotten?