A resourceful boy and his friends discover a mysterious deer and, when odd incidents begin to occur, organize themselves into a club to investigate. The story follows their day and night searches, clue-gathering, and stakeouts—examining disturbances in gardens, a distinctive heel-plate clue, a lassoed capture, and an eventual escape—while they set traps and mount a final effort to resolve the puzzle. Episodes alternate between playful pastime and tense sleuthing, testing the youngsters’ courage, cooperation, and problem-solving until they identify and confront the cause of the mystery.