The Case Of The Singing Violin is a Sherlock Holmes television movie from 1955.
It stars Ronald Howard as Holmes, H. Marion Crawford as Dr. Watson and Archie Duncan as Inspector Lestrade.
A young woman is seeing visions and her harsh stepfather is trying to get her institutionalised.
Then her husband-to-be is murdered as he’s on his way to see Holmes, who immediately knows the murderer is the stepfather.
As always, he’s correct.
Movie pages here.