Oil! by Upton Sinclair

Back in Paris, and there were long letters from Verne; the government had filed suit for the return of its oil lands, and the Sunnyside tract was in the hands of a receiver, and all the development stopped. But they were not to worry -- their organization would be put to work on the various foreign concessions, and as for the money, what they were getting out of Paradise would keep them in old age.

Strange to say, Dad worried scarcely at all. Mrs. Olivier had discovered a new medium, even more wonderful than the others, and this Polish peasant woman with bad teeth and epilepsy had brought up from the depths of the universal consciousness the spirit of Dad's grandfather, who had crossed the continent in a covered wagon and perished in the Mohave desert; also there was the spirit of an Indian chief whom the old pioneer had killed during the journey. Most fascinating to listen while the two warriors told about this early war between the reds and the whites!