Sredni Vashtar

"Sredni Vashtar" is a short story written by Saki (Hector Hugh Munro) between 1900 and 1911 and first published in his 1912 book The Chronicles of Clovis. 

Conradin, a sickly 10-year old boy, lives in the care of his despised, overbearing and controlling cousin Mrs De Ropp. He relies on his vivid imagination not only to keep him strong enough to survive, but also to serve as his escape from the real world. Rebelling against Mrs De Ropp's oppressive care, Conradin secretly keeps two animals in an unused garden shed: a hen, which he adores, and a polecat-ferret, which he fears and keeps locked in a hutch. Gradually, Conradin begins to venerate the ferret as a god, naming it Sredni Vashtar. He worships it weekly, bringing offerings of flowers and berries, and stolen nutmeg for special occasions.