Jack Armstrong #11

When Uncle Jim's experimental nuclear ray clears the jungle to reveal the legendary lost city of Comalpotec, Jack Armstrong and his team descend to explore the ancient Maya ruins—only to discover that their guide, Colonel Gonzales, has betrayed them for a chance to seize both the ray machine and the city's fabled treasure. Trapped in the sacrificial temple's depths and forced to overcome jungle dangers, Jack and Billy must find their way back to the surface before Gonzales can eliminate Uncle Jim and Betty.

Vic Hardy of the Scientific Bureau of Investigation tackles a wave of suspicious car collisions when a pattern emerges: insurance claims spike while a Lancaster automobile plant boasts superior durability. Using X-ray analysis on crash debris, Vic uncovers a sinister scheme and goes undercover at a garage to smoke out those behind the racket. The investigation turns into a dangerous chase as Vic closes in on criminals operating one of their own rigged vehicles.

Billy Fairfield heads to a winter carnival at Dartfoot College with his pal Horace, where he spots a young woman named Merrie and attempts to impress her on the ice—with hilariously disastrous results. When Horace learns that Merrie prefers the jitterbug type, he schemes to get Billy into a dance contest where he might win her over, leading to an unexpected turn of events on the dance floor.

When Betty visits Alaska for the annual Alaskan Trappers Contest, she and her friend Connie find themselves thrust into an unexpected rescue when contestant Ralph Carter runs afoul of a protective mother bear near Lake Hecate. Betty joins the search party to help, and together they must navigate both the treacherous wilderness and the animal's fierce instinct to save Ralph and complete the competition.

Jack Armstrong has a crew race to prepare for, but when his uncle arrives with government business and introduces him to the Professor's daughter, a routine trip to a secret lab on Randall Island turns into a desperate rescue—and uncovers a dangerous theft that threatens the nation. With stolen explosive formula papers in the wrong hands, Jack must use his wits to set a trap that could cost him the big race, but might just save the day.