Clay is a young man in a small town who witnesses his friend, Earl, kill himself because of the ongoing affair that Clay was having with the man's wife, Amanda. Feeling guilty, Clay now resists the widow when she presses him to continue with the affair. Clay unknowingly befriends a serial killer named Lester Long who murders the widow in an attempt to "help" his "fishing buddy."

Stiff Upper Lips is a broad parody of British period films, especially the lavish Merchant-Ivory productions of the 'eighties and early 'nineties. Although it specifically targets A Room with a View, Chariots of Fire, Maurice, A Passage to India, and many other films, in a more general way Stiff Upper Lips satirises popular perceptions of certain Edwardian traits: propriety, sexual repression, xenophobia, and class snobbery.