[2] Dr John H. Watson becomes convinced that his friend Sherlock Holmes, the famous private detective, is delusional—particularly in his belief that the renowned mathematician Professor James Moriarty is a criminal mastermind—as a result of his addiction to cocaine.

"[6] Gene Siskel of the Chicago Tribune gave the film four stars out of four and called it "the classiest motion picture of the holiday season" and "a rare combination of money and brains.

Producer-director Herbert Ross and writer Nicholas Meyer, adapting his novel, have fashioned a most stylish, elegant, and classy period crime drama.

"[9] Charles Champlin of the Los Angeles Times wrote, "It is a particularly handsome period piece, beautifully staged and acted and most genuinely charming.

"[10] Gary Arnold of The Washington Post called the film "an amusing, elegant, and unusually appealing adventure movie, a swashbuckler with literate, intellectual heroes.

He shared a story about how he and Ross decided to cast Duvall "in revolt" against Nigel Bruce's portrayal of Watson as a "Colonel Blimp"-type character.