Gaudy Night is a 1935 Lord Peter Wimsey detective story by Dorothy L. Sayers. It is the third of the Wimsey novels to feature Harriet Vane.
It was adapted for television in 1987 as part of a series starring Edward Petherbridge as Lord Peter and Harriet Walter as Harriet Vane.
Having been acquitted of murder, Harriet Vane attends a reunion at her (fictional) Oxford alma mater, Shrewsbury College. Here she encounters a tangle of poison pen notes, obscene graffiti, and dangerous pranks that Lord Peter helps her solve.
As the case develops, she begins to realize that she loves Wimsey, who has been proposing to her ever since he first met her (in prison, facing the gallows as a suspect in the murder of her former lover, in Strong Poison), and she finally accepts his proposal of marriage.
Their marriage and honeymoon (interrupted by yet another murder mystery) is depicted in Busman's Honeymoon.
The plot of Gaudy Night was adapted to become the two-part Out of the Past episode (#155 & #156) of the American television mystery series Diagnosis Murder starring Dick van Dyke as Dr. Mark Sloan.
The episode first aired on 11 May 2000, with John Schneider as the villain.Synopsis
Warning: Wikipedia contains spoilers