The Fraggle Horn is stolen from the Great Hall, shortly before the World's Oldest Fraggle intended to call a meeting to host a party in honor of Uncle Traveling Matt. Inspector Red (clad in a Bogey-style fedora and trenchoat) is on the case to determine who took it. She soon finds herself rashly accusing several denizens of the Rock in turn, each with an ostensible motive for taking the horn: Traveling Matt himself (embarrassed over the loss of his hat and toupee), Boober (who cares little for the noise and frivolity of meetings and parties which the horn represents), and Marlon (who lost his lucky pebble in it).
In a variation of drawing room mystery cliches (especially in 1930s and 1940s movies), the suspects are gathered in the Great Hall, Inspector Red announces "You're all probably wondering why you've been called here today" and finally uncovers the guilty party.
Meanwhile, in Outer Space, Doc suspects Sprocket of eating all the peach and praline ice cream. Uncle Matt's own Outer Space adventure (in flashback rather than postcard) takes him to an Ontario racing car speedway.