Mr. Holmes (aka A Slight Trick of the Mind)

Set in 1947, a long-retired Sherlock Holmes lives in a sleepy village outside of London with his housekeeper and her amateur-sleuthing son. With his legendary mental powers on the wane and minus his sidekick Watson, Holmes becomes haunted by an unsolved case from 50 years ago where he remembers only fragments: a confrontation with an angry husband and a secret bond with his beautiful but unstable wife.