Despite being so-called friends and fellow members of the Junior G-Men Club, teenagers Penrod Schofield and Rodney Bitts are constantly at odds with each other, their latest kerfuffle which has threatened Penrod's father Frank Schofield's long awaited raise at the bank in his boss being Rodney Bitts, Sr. Despite this latest row being precipitated by Rodney, Mr. Schofield, in only knowing the end result, ends up grounding Penrod. Penrod, able to break out of his room and out of the Schofield house, ends up going missing. Penrod's missing status changes the relationship between Mssrs. Schoefield and Bitts who band together, along with others, to offer a reward for Penrod's return, a reward that nonetheless places the Schofields deep in debt. Carnival performer Tex Boyden, knowing what happened to Penrod in having seen him in the basket of a hot air balloon that broke loose and floated away to parts unknown, believes he has a way to obtain the reward money as Danny Dugan, who works for fellow carny Professor Caligostro, is the spitting image of Penrod, Danny who Tex can present to the Schofields as their long lost son Penrod who can't remember anything about his life in suffering from amnesia. In a double con, Professor Caligostro concocts a story which has Tex shut of the plan in the Professor bringing Danny to the Schofields to keep the reward money for himself. The Schofields indeed do believe that Danny is their son. The situation gets more complicated when Tex arrives on the scene threatening to expose the con unless he gets his cut, and as Penrod himself tries to make his way back home. What happens in the matter is affected by the work of the Junior G-Men working in part on the fact that Penrod's faithful dog, Duke, can tell that Danny is not Penrod.
—Huggo