sentences:  The story follows Is from London to the fictional town of Blastburn in the north of England, in her quest to discover the mystery behind the disappearance of many London children and to track down two missing boys in particular.Like the rest of the books in this series, "Is" takes place in an 'alternative history' version of the early nineteenth-century and has elements of steampunk and magical realism.Is Twite, a character introduced in "Dido and Pa" as Dido's previously unsuspected half-sister, is now living on Blackheath Edge near London with a third, older sister named Penelope (called 'Penny') and their cat, Figgin.