 In 1814 , Mary began a romance with one of her father 's political followers , the then married Percy Bysshe Shelley . Together with Mary 's stepsister Claire Clairmont , Mary and Shelley left for France and traveled through Europe . Upon their return to England , Mary was pregnant with Percy 's child . Over the next two years , she and Percy faced ostracism , constant debt , and the death of their prematurely born daughter . They married in late 1816 , after the suicide of Percy Shelley 's first wife , Harriet . 
