The story is a flashback: a middle-aged Englishman revisits his childhood street and recalls events which happened when he was seven. Of course, since Neil Gaiman is the author, these events are supremely supernatural, weird, and not entirely explainable. The boy’s new nanny turns out to be an other-dimensional being which considers mankind an amusement at best, who hitched a ride by burrowing into the boy’s foot and up into his heart. And she’s actually pretty benign compared the the “cleaners” or “varmints,” whose role is to clean up entities from other planes of reality who don’t belong it their current locale. With all the scary stuff out there though, luckily old Mrs. Hempstock and her granddaughter Lettie (both eternal despite their apparent ages) are vigilant in their defense of humanity.