In one letter to Mrs.Gisborne she compared the journey of herself and Jane to Pisa and Leghorn to get news of Shelley and Williams to that of Mathilda in search of her father, "driving--( like Matilda), towards the _sea_ to learn if we were to be for ever doomed to misery."[x] And on May 6, 1823, she wrote, "Matilda foretells even many small circumstances most truly--and the whole of it is a monument of what now is."[xi] These facts not only date the manuscript but also show Mary's feeling of personal involvement in the story.

In the events of 1818-1819 it is possible to find the basis for this morbid tale and consequently to assess its biographical significance.
On September 24, 1818, the Shelleys' daughter, Clara Everina, barely a year old, died at Venice.

Mary and her children had gone from Bagni di Lucca to Este to join Shelley at Byron's villa.

Clara was not well when they started, and she grew worse on the journey.

From Este Shelley and Mary took her to Venice to consult a physician, a trip which was beset with delays and difficulties.