While spending Christmas break at an Arizona dude ranch, Trixie and the Bob-Whites work to solve several mysteries--a phony cowboy, disappearing staff, and puzzling cries in the night.
Not long after her family becomes wealthy, Diana Lynch's long-lost uncle appears and starts ruining her social life, causing Trixie Belden to investigate whether Uncle Monty is an imposter out to steal the Lynch fortune.
When Trixie Belden and Honey Wheeler find a cut diamond embedded in the dirt floor of the old abandoned gatehouse, they set out to find whoever left it there.
After a storm blows through Sleepyside and damages the Bob-Whites' clubhouse, Trixie and Honey take a job patrolling the game preserve and find evidence of a poacher.