"Gaudy Night" was the second of Dorothy L. Sayers's "Lord Peter Wimsey" detective novels to be written with the action and plot seen through the eyes of Harriet Vane rather than Wimsey himself. When transferred to the screen, this results in poor Wimsey being relegated almost to a supporting actor. Apart from one or two brief introductory appearances, he appears only in the last half of the series.
Still, the plot holds things together quite well. Detective novelist Harriet Vane has lived down the notoriety of having been accused of murdering her lover. She accepts an invitation to revisit her alma mater, a ladies' college in Oxford. Shortly after she renews her acquaintance with her former fellow-students and tutors, someone starts playing distasteful pranks around the college. The Warden and the other dons ask Harriet to investigate. Wimsey, her suitor, joins the investigation when the practical jokes become more dangerous. Finally, there is the long-standing romantic tension between Wimsey and Harriet to resolve.
Edward Petherbridge plays Wimsey very much in the style set by Ian Carmichael in the 1970's. However, Harriet Walter, as Harriet Vane, rather steals the show.
This is definitely not a stock "Whodunnit". Without laying it on with a trowel, "Gaudy Night" highlights the difference in attitudes between a withdrawn set of cloisters which need deal only with matters of philosophy and theory, and the "real world", with practical problems to face and overcome. This gulf is emphasised by the cut-glass accents and precise diction of the dons and students, and the "common" speech of the college servants and other inhabitants of Oxford, where they appear.
Worth both watching and reading.