This story was first published in the Civil and Military Gazette on 24 January 1887, and collected in the first edition of Plain Tales from the Hills in 1888 and in subsequent editions of this collection.
Moriarty, a 'big, dark, abstracted man', and a civil engineer, has spent four years in virtual isolation and seriously taken to drink. He is going downhill fast. Then he meets the fascinating and notorious Mrs Reiver, and convinces himself that he must make himself worthy of her friendship. With an agonising effort he successfully fights his addiction for her sake, though she never knows of it. He has been 'in error' about her all along. As Kipling says: 'he thought her something she never was, and in that belief saved himself'.
As Norman Page points out in A Kipling Companion, this is one of a group of stories on self-delusion - here of a beneficient kind. Other treatments of the same theme, of different degrees of seriousness, include "Wressley of the Foreign Office", "Venus Annodomini" and "In the Pride of his Youth".