With a distractingly dressed Parsley in tow, since Amelia is off on 'Witch Business' of an unknown nature, Zahn heads for the old tree that marked the center of the original, pre-dam Wingnut territory. The old map he has isn't a lot of use, since so much has changed in seven decades, but he chooses a likely tree and starts climbing, leaving Parsley on the ground.
The Kadie finds an old cabin, and its door handle has the same combination-key buttons as in the underground apartments, which makes Zahn hopeful. He ends up having to kick the door in because the hinges are warped. Inside he finds an old trunk-bed and a built-in desk. He investigates the old desk first, finding a false bottom. Inside are a metallic-glass chisel with a homemade handle (which has some sort of image embedded in it) and even one of the underground key-cards but he can't tell if it's the same as the one he has.
The trunk gives him a shock, since inside he finds the body of a troll! Or rather, a very good troll costume. He takes that, revealing some junk and an erotic wood-cut underneath. He also uncovers a fake, ceramic knot that reveals a peephole for spying on a neighboring cabin (now just a frame).
Zahn goes to check the other cabin out, and finds initials-in-a-heart carved into the doorframe (meaning they were carved after the cabin was already dismantled). They read 'A W + C K', which hints that Abner had a crush on a Kettenrad! Zahn plans to find out who 'C' Kettenrad was.
Back below, Parsley is waiting with lunch (and more) ready, and wears out Zahn for a bit. Afterwards, he shows her the diagram in the chisel handle, and the Lapi recognizes it as 'nut sign' a code Amelia and her used to record where they buried treasure as children. Apparently it's an old Kadie art. She helps decode it, leading the pair towards Abner's secret workshop.
It's only when they're almost there that Parsley remembers that the river in the diagram is now the reservoir. The workshop entrance is underwater!