On July 8, 1822, Mary's life was forever altered when her husband was drowned at sea in a boating accident off the coast of Livorno (sometimes called Leghorn), Italy. By now, her life was seemingly connected to tragedy, with the deaths of three children, her mother, and her husband, and the suicides of Percy's former wife and Mary's half-sister.
She spent the rest of her life writing original works and tending to the works of her late husband. She became the keeper of Percy Bysshe Shelley's fame and was editor of his posthumous works. This was done to raise the necessary funds to support herself and her son. In 1824, Posthumous Poems was published, which was edited by Mary. She had begun negotiations with her father-in-law, Sir Timothy Shelley, who did not want his son's works published or his family's name published in the press again during his lifetime. The Last Man (1826) is Shelley's best-known work after Frankenstein because it tackles the subject of mass catastrophe in society.
In 1841, her son graduated from Trinity College, and he asked his mother to accompany him on a tour of Italy and Europe. During her travels, she compiled notes about her travels. Her son married in 1848, and Mary lived with him and his wife until she died. On February 1, 1851 Mary died in London and was buried in Bournemouth, England.
