The Pumpkin Child — Nancy A. Collins

Hollis Railsback returned home from World War Two to find both his family business and his high school sweetheart stolen by the same man: Virgil Bayliss. Hollis had always envied Virgil's luck: everything seemed to come so easily to him, while he had to fight for everything he had.

Then one night,after taking a wrong turn on an old dirt road, Hollis finds himself at the shack of Granny Grimes, the old witchy-woman who lives in the middle of a pumpkin patch. Granny Grimes offers to swap his luck with that of Virgil--but once his luck is changed, he can never switch it back. The very next day his luck begins to while, at the same time, Virgil Bayliss contracts polio.

But, after years of good fortune in business and love, when he and his wife experienced trouble having children, Hollis decides to push his luck yet again--with disastrous consequences that finally come to a head on Halloween night.