While exploring Dragon's Mouth Cavern, the Boxcar children encounter a group of suspicious, unfriendly people, including a man who refuses to identify himself, Mr. Pitt and Mr. Lyme who try to scare the young sleuths away, and Crystal Hollowell, who lies about where she works. Simultaneous.

שם הספר
Snowbound mystery
Surprise island
Bus station mystery
Bicycle mystery
The woodshed mystery