Twelve-year-old Kess and her older brother, Oliver, have lived alone in the Unnatural History Museum ever since Mam and Da left for Antarctica on a research trip ever so long ago. Well, there’s also Shrunken Jim, a pickled, disembodied head Kess carries around in a jar, a staunch if unusual friend. Kess hopes that new exhibits will revitalize the museum, and when newcomer Lilou visits, Kess finds a partner in exploration—and what they learn in Eelgrass Bog upends everything Kess thought she knew. Averling’s worldbuilding is deft and beguiling, from Kess’ unfamiliarity with modern tech that tells readers something’s very amiss to the delightful weirdness of the museum and its environs. Averling’s use of the present tense effectively unmoors readers (as well as Kess) from time, and Kess’ voice is a delight. “Oh, vermin,” she curses, and she dismisses Oliver as “a prune-hearted cockroach.” Shining brightest is her endearing relationship with Shrunken Jim—an excellent supporting character for all that he’s brined. Most human characters are cued white; Lilou has two dads, and Kess and Lilou find that they might “like-like” each other, though active romance is left for Kess’ future.