Danny and Rex perform daring high-wire tricks for charity in a circus floating on a barge. But someone is sabotaging the circus, shooting pellets at the lions to enrage them, setting a fire to the canvas, and even planting a bomb on the paddle wheel! Rex and Danny stop every threat and expose the strong man who lost out on a prize.
Bobo's latest craze is spearfishing with SCUBA gear. But a fellow spearfisher is clubbed to death and there are three suspects. Nobody listens to Bobo, so he swims after a diver and finds an underwater grotto with a Spanish treasure. Bobo dives to avoid getting speared and the Sheriff takes the diver into custody. The dead man refused to split the treasure. Bobo decides to stick to dull checkers. "A fellow can't get killed dead while playing it!"
In eastern Tennessee, Danny and Rex accompany Professor Barrett (last seen in "Valley of the Thunder King"). He plans to view a total eclipse of the sun. The local "hillbillies" won't guide them up Big Spooky Mountain, claiming it's haunted, until Rex saves a child from a runaway carriage. Up on the mountain, by night, Rex battles a lynx while the Professor is nabbed by ghosts of Civil War soldiers! Rex bowls them over - three convicts hiding out who found a Civil War stash.