Milo and Iris, two apprentices at the Silver Creek Post Office, encounter the crystalline sugar-like contaminant jamming the mail sorting machinery. The contaminant's thermal adhesion properties are causing localized freezing and sticking. Drawing on shared world knowledge about historical stabilization agents, Iris suggests using a material resistant to cold lock, recalling the felt used on the silver bells. They locate a tin of Mica Dust Stabilizer in a rarely used supply locker. The Mica Dust, known for its non-conductive and insulating properties used previously in the Observatory Annex, successfully neutralizes the crystalline residue, clearing the jam. As the mail resumes flow, they discover a single, unusually warm, crimson envelope sealed with dark wax bearing a silver star, addressed simply to the Keepers of the Warmth. The letter is postmarked from the Municipal Greenhouse, setting up the next investigation.