Turn Left at the Cow by Lisa Bullard

Travis runs away to stay with his dead father's mother in Minnesota. He never knew his father, but Travis discovers that he died after breaking into a bank. When some of the stolen money turns up, everyone assumes Travis found it. Kenny and Iz were already searching for the money, so they decide to team up with Travis to find it. However, Travis receives a threatening note, and the adventure suddenly gets dangerous. Is it from the crazy man living at the dump or someone else? Or is it possible that Travis's father is still alive?

The plot developed into a decent mystery with many suspects to choose from. The solution was a surprise. Travis and Iz had family problems, and that may have helped to bring them together.