The back matter of the 1995 Bantam edition of this book includes an exchange of correspondence between Stout and his editor at Viking Press, Marshall Best.

Byne claims to have a cold and is unable to attend; although skeptical, Archie agrees to stand in for him, despite Mrs. Robilotti's being a former client of Nero Wolfe's who bears him a personal dislike.

Alone of the guests, Archie maintains that Faith Usher did not commit suicide, claiming that he observed her constantly throughout the evening and that she never had an opportunity to pour the cyanide from her bottle into her glass.

Although the authorities and the other guests pressure Archie into changing his story, Nero Wolfe believes him and decides to settle the matter by solving the case himself.

Although Wolfe's investigation begins unpromisingly, he becomes convinced that his suspicions are correct when the police receive an anonymous tip revealing Laidlaw's secret.

Byne admits that he knew that Laidlaw was the father of Faith Usher's child, and claims that he had them both invited to the dinner without their knowledge as a spiteful prank.

During their conversation, however, Orrie Cather infiltrates Byne's apartment and discovers a letter revealing that Mrs. Robilotti's deceased first husband, Albert Grantham, was the father of Faith Usher.

This demonstrates that Mrs. Robilotti's son Cecil, who gave Faith the poisoned champagne, had a routine way of handing over a glass that someone who knew his habits would be able to predict.

Mrs. Robilotti murdered Faith to conceal the secret and out of resentment over her husband's affair and, learning that she was in the habit of carrying cyanide, acquired some from another source to make it look like a suicide.

Lee Goldberg and William Rabkin adapted Champagne for One for the second episode of the A&E TV series A Nero Wolfe Mystery (2001–2002), a Jaffe/Braunstein Films coproduction with the A&E Network.

Other members of the cast (in credits order) are Bill Smitrovich (Inspector Cramer), Colin Fox (Fritz Brenner), James Tolkan (Mr. Hackett).

Reid (Sergeant Purley Stebbins), Christine Brubaker (Rose Tuttle), Steve Cumyn (Cecil Grantham), Boyd Banks (Austin "Dinky" Byne), David Schurmann (Robert Robilotti), Michael Rhoades (Beverly Kent), Janine Theriault (Ethel Varr) and Patricia Zentilli (Faith Usher).

Set in 1959 in Rome, where Wolfe and Archie reside after leaving the United States, the series was produced by Casanova Multimedia and Rai Fiction and directed by Riccardo Donna.