After wrangling permission from her parents and a grudging acceptance from the director of the expedition, Julie is allowed to spend her summer at some archaeological digs in New York state, where she is gainfully employed as a digger-artist-mapmaker. With the disappearance of an ancient Indian mask, the mystery of the stolen artifacts is underway. Since Julie blames herself for the second robbery, she takes a dangerous chance in following a prowler into the woods late at night. Her close brush with death teaches Julie and her cohorts that their elusive tormentor is a pretty determined fellow and, as all clues indicate, a member of their own group. Is it Rus, the practical joker, or Clint, the serious scientist, or Dr. Battino, who is in need of money? As tension mounts, the reader too becomes a detective until Julie's final encounter with the culprit, a fast battle and victory for the diggers. A competent mystery.