The Sky Chart tells the story of Twig's birth from Tweezel's perspective. Quint is in urgent need of money to repair the Stormchaser. He takes a job offered to him by Multinius Gobtrax. Maris, his wife, comes along. When they discover that Maris is pregnant, they try to prevent Gobtrax from noticing it. They are about to return to Undertown when Maris is forced to abandon her child in a woodtroll village in the Deepwoods. Quint does not have access to the sky chart with which he could locate the woodtroll village. Maris and Quint split up in their grief and feverish search for their lost child.