From the Valley of the Missing (1970)

A baby is left on the Brinbecombes' yacht while they are sailing up the Hudson River, and they adopt him and name him Everett. They are neighbors of Governor Floyd Vandecarm whose twin children, Floyd Jr. and Fledra, were kidnapped in early infancy. Their abductor was Lon Cronk, a man sent to prison by Vandecar when the latter was a district attorney of the county. The twins grow up in Cronk's shack as "Flea" and "Flukey." Despite her rough surroundings Fledra/Flea grows into lovely young womanhood and she and her brother run away from Cronk's cruelty. They reach Tarrytown and peer into the lighted windows of the home of siblings Horace and Anne Shellington. Anne brings the two young vagrants into the house and ultimately adopts them. But Cronk, aided by Everett, wages a long, evil campaign to regain possession of the children.