Guaranteed—Forever!

"Guaranteed—Forever!" by Frank M. Robinson is a science fiction story that unfolds in post-war America as it tells of Manning, a dedicated investigator of mail-order scams, who stumbles upon an unbelievable carburetor that supposedly runs on water, promising amazing gas mileage. As Manning looks into the Forsythe Carburetor Company, he finds a complex web of deceit, suggesting that Forsythe's scams might hide something greater and very alarming. The stakes rise when Manning barely avoids getting attacked by Forsythe’s partner, making him doubt the realness of the carburetor. The story takes a strange turn when Forsythe's true intentions are revealed, pointing to the possibility of time travel, a fact that challenges Manning through the existence of a vial labelled "Forsythe's Cancer Cure" and a dire, real hope.