All’s Well That Ends Well, by William Shakespeare

Introduction

[from Wikipedia]

All's Well That Ends Well was probably written later in Shakespeare's career, between 1601 and 1608.

The five acts follow the action of Helena, a lowborn beauty, who pines for the son of her guardian, Count Bertram. She is granted his hand as a reward for curing the King, but Bertram runs away to war, declaring “When thou canst get the ring upon my finger which never shall come off, and show me a child begotten of thy body that I am father to, then call me husband.” Helena tricks him into giving her his family ring and sleeping with her, by posing as Diana, the virginal daughter of a widow. These were his conditions for being her true husband and he agrees to be a good husband in the final act.

Shakespeare's source is most likely a story in William Painter's The Palace of Pleasure, which was in fact a translation of the ninth story from the third day of Boccaccio's Decameron.