As with Sabriel and Shade's Children, Nix immediately sets the stage for the primary conflict in The Fall: Tal's desperate need for a primary Sunstone for his family. A primary Sunstone enables a family to ascend to the shadow realm of Aenir with the rest of the inhabitants of the Castle. The ascension is an annual event during which Tal will exchange his shadowguard, a low-level spirit mimicking his original shadow, for a stronger Spiritshadow that will be his companion for the rest of his life. All children ascending to adulthood at the age of thirteen and three-quarters eagerly anticipate the Day of Ascension.

Tal's family Sunstone disappeared with his father, Rerem, while on a mission for the Empress. His mother Graile's Sunstone is weakened by her long illness, and his uncaring aunts refuse to share any of their Sunstones. Tal tries to win a Sunstone by honorable means, competing in a contest held every quarter to recognize the development of skills in the Chosen, the people of the Castle. Tal signs up for an Achievement of Body, a test of physical ability, but at the last minute he finds out his name has been listed for the Achievement of Music instead. When he sees Shadowmaster Sushin take a seat as a judge, he knows Sushin changed his name on the lists, since Sushin hates Tal's family for reasons unknown to Tal. As a result, Tal fails. His only option is to steal a Sunstone from the nets strung above the Veil.