The Curious Tale of Wisteria Vale is the script of a play written in Common. It is split up into three acts, telling the story of a heroic bard before he becomes corrupted by evil. A wizard named Ryllia Liadon donated the book to Candlekeep as an entrance gift. She didn't tell the Avowed that the book contains the secret to accessing Wisteria Vale, a magical demiplane created by the Harpers to imprison a bard named Arrant Quill until they could free him from the influence of an evil artifact. The book has been hidden in the Candlekeep archives for three years, but the Harpers have finally discovered a cure for Quill's corruption, and the time has come to visit Wisteria Vale once more.

This adventure can be used in any setting that features landowning nobility as a social class. It focuses on the Firebird, a mythical creature from Slavic folklore similar to the phoenix. The characters begin inside a tailor’s shop where they’ve been gathered by Pero Toporov, the best tailor in the city of Krylo. The city is ruled by the confident and insensitive Baron Yuri, who commissioned Pero to create a beautiful cloak woven with the feathers of the Firebird, a creature known for its healing powers. Pero agreed on the condition that their work would be used to aid Yuri's citizens, who have been sick and ailing under Yuri's restrictive rule. Instead, the Baron took the cloak for himself. Pero is hiring the adventurers to help them break into the Baron’s fortress and steal the cloak back without being caught. The characters find a way inside the fortress and break into the dungeon, where the cloak is supposedly hidden away. Within the dungeon, the party finds the Firebird itself locked in a golden cage where Baron Yuri—wearing the magic cloak—is antagonizing it. Baron Yuri attacks them to protect his treasure and is not open to negotiation. However, the characters may try to befriend or capture the Firebird. If they sway the bird to their side it may help them fight the Baron. Once Baron Yuri is defeated, the characters can take the cloak for themselves or return it to Pero. Dethroning the Baron earns them the gratitude of the city’s people. If they return the cloak, Pero pays the adventurers and assures them that the cloak will be used for good from now on. Pgs. 173-179