A young miner steals a pony sold for slaughter and with Vicky's help hides it at Dr. Gordon's. The owner soon finds the pony and makes trouble for the young pair.

While riding Black Beauty, Vicky and Kevin encounter a threatening recluse at the Abbott farm. Despite being warned by everyone to stay away, the children persist in trying to solve the mystery. When a runaway horse endangers young David Abbott, the children get their answer.