It was fall. And on the night of the big frost, Henry and his dog, Laird Angus McAngus, decided that they must explore the wild and untracked mountains near their house. Before winter set in. So the next morning they set out, with flags and banners as any good explorers would, and also rope. "You always need rope when climbing in the mountains - for safety," Henry said. "I expect you to be home before dark," said Henry's father. And off they went. They picked their way through dangerous canyons and up steep cliffs, had their lunch, and then trouble began. It proved to be an exciting afternoon for Henry and Angus, much better than Henry's imagination could have made it.