Patient of Promise, by E.C. Tubb (epub/Kindle)
In a long career, Edwin Charles Tubb (1919-2010) published 120 novels, and 200 short stories, mostly science fiction, but including historical, detective, and westerns. Guest of Honor at the 1970 World Science Fiction Convention, some of his finest SF short stories were collected in The Best Science Fiction of E. C. Tubb (Wildside Press, 2003).
"Patient of Promise" originally appeared in Authentic Science Fiction #82, July 1957 issue.