When the FBI suddenly orders Judy's husband Peter to Washington, D.C. on a bank robbery case, the young couple is just about to start off on a trip. To cheer herself up after Peter's plane departs, Judy buys a corsage of snapdragons. Judy is wearing the corsage when she and Peter's sister, Honey Dobbs, decide to drive to New York City and spend a few days with Irene and Dale Meredith. On the way, the two girls nearly have a fatal accident. A handsome young stranger comes to their rescue and introduces himself as Mr. Nogard. What Mr. Nogard says when he sees Judy's corsage, and the mysterious package he gives her, lead to an exciting cross-country ride for Judy and Honey. In the heart of Yellowstone Park, at the Dragon's Mouth, Judy finds a vital clue to Peter's bank robbery case and at the same time places herself in great danger. How one word on a postcard alerts Peter to her predicament winds up a hair-raising mystery-adventure for Judy.