Pedro, a strange Mexican boy accompanied by a ferocious dog, Shag, appears at the Bar L, hoping to capture a white stallion which has challenged Golden Boy, leader of the herd, for supremacy. Charlie Carter, who lives at the Bar L, befriends Pedro and upholds him when he is charged with murder. Fifth in the Golden Stallion series, this is another mystery-western in which the author conceals just enough from his reader to keep him peeping into the next chapter. Charlie clears Pedro's name with Shag's help. This will satisfy old Montgomery fans and place a few new ones in his corral.