Mr. Trepid looks for understone funds and forces Z to make a map while Z makes a fake map. Z is a good guy because he is friends with Tiller and Sairy. Also Z marks the stones in the holler to make them look special.
When they are on their fake trips, Florida and Tiller get their boat flipped over and Tiller has a bad heart attack. Also, Sairy and Dallas get lost on their hike. Dallas has a weird feeling Florida is in trouble so they find Z who drives them to Florida who pulled Tiller out of the water.
When they all get back from their trips they find out that Mr. Trepid is looking for their understone funds, but they trick Mr. Trepid using Z's help into thinking he found real diamonds when he really found fake diamonds.