Treasure Hunter, Book Two of Dunsmuir Boy

Leif has left Dunsmuir to attend college. On his first return home he reunites with his friends and they once again engage in the activities of swimming and hunting, even though Leif now has a girlfriend, earning the envy and teasing appropriate to recent high school graduates. The relationship between Leif and his girlfriend is frequently strained by Leif's other relationship: the one with time. The concept of "tomorrow" is sometimes not readily apparent.
As Leif and his friends catch up with one another and swim until the water turns too cold, they reminisce about a story of a strong box of gold stolen by Indians and hidden in a not-too-distant granite fortress-like formation. They are certain the ancient tale is true and set out one morning to find the gold. They discover the granite fortress is much larger than imagined from below and not forgiving of impetuosity or willing to reveal secrets.
In the lengthy, charming, and moving coda, the concept of time is viewed by a boy who becomes a man between one full moon and the next.