The Bobbsey Twins in a TV Mystery Show

When the Bobbsey twins fly to California to be in a television show, they have no idea they will find a mystery awaiting them.

During rehearsals, they befriend a beautiful, long-haired dog who has been specially trained for the show and discover a tiny key in his fur. Suddenly the dog disappears from the set without a trace. Everything is in a dither. Did he run away or was he stolen?

The twins are sure that they key is their first clue to the mystery. But what does it open? Their clever investigation and fearless persistence help them uncover the animal's secret and results in the capture of a ring of unscrupulous thieves whose works spreads far beyond the state of California.