In this 16th volume in the series, The Motor Boys on Road and River, some of Jerry's widowed mother's investments have been doing a bit poorly lately and she has decided to sell some of her land—specifically, some swamp land—for which she receives and accepts an offer that seems too good to be true. And you know what they say. . . . Turns out the land has a deposit of clay that has unique medical properties, and the offer for her land is actually well under its actual value. Moreover, the boy's old sidekick, Professor Snodgrass, gets hoodwinked into writing a testimonial for the crooks. The boys work diligently to overturn the sale, even while Professor Snodgrass falls off a cliff and, once the boys find him, requiring a delicate brain operation if he is to survive.
