A few month's later. however, Shelley gave his father even greater cause for alarm. In August 1811, he eloped with Harriet Westbrook, who as the daughter of a coffee-house owner was of a decidedly inferior station to the aristocratic lineage the Shelley family claimed. Although Sir Timothy settled enough income on the young couple for their modest comfort, he refused ever to see his son again, instead handling all their relations through his London solicitor. Shelley, in a kind of retailation, set about finding a substitute for his removed and unsympathetic father, alighting in 1812 on the renowned radical intellectual, novelist, and philosopher William Godwin to whom Shelley introduced himself in rather the later guise of Victor Frankenstein, as an admirer of the occult writers Cornelius Agrippa and Paracelsus. Although Godwin disapproved of his agitation, Shelley set out to effect a Godwinian revolution in Ireland, traveling later this year with Harriet, and her older sister Eliza Westbrook, to Dublin, where they circulated pamphlets calling for greater political rights for Roman Catholics and autonomy for Ireland.
By 1813, Shelley had settled in London, where he printed his first major poem, Queen Mab. In June of that year, Harriet gave birth to their daughter Ianthe. As the year wore on, however, relations between Harriet and Shelley deteriorated seriously, and Shelley came to regret the impulsiveness of his marriage. It was in this state of frustration and emotional duress early in 1814 that Shelley, on a visit to Godwin, became reacquainted with his sixteen-year old daughter Mary, herself just returned from a prolonged stay in Scotland. Soon the two of them had fallen in love. On 27 July 1814, they fled to the continent along with Mary's step-sister Claire Clairmont, and for the ensuing month-and-a half they traveled through France, Switzerland, and Germany in a journey later memorialized as a History of a Six Weeks' Tour.
Upon their return in September harsh reality quickly intruded on the couple's idyll. Shelley found himself shunned by Godwin and dunned by creditors. With Mary now pregnant, Harriet Shelley gave birth to a second child, whom she named Charles, on 30 November 1814. In so confused a family situation, Shelley at last gained financial relief when his grandfather, Bysshe Shelley, died in January 1815. Shelley now began to receive an annual income that allowed him to escape many of the financial problems that had plagued him since his marriage. In these improved circumstances Shelley and Mary settled in Marlow near Windsor, where they were close to his friend, the poet and satirical novelist Thomas Love Peacock. In that year he wrote "Alastor; or, the Spirit of Solitude," which was published the next March
In January of 1816 Mary gave birth to a son, whom she named William after her father. Later that spring Shelley, Mary, and Claire once more set out for the continent, this time rather from necessity. During March Claire, through an improbable but successful act of rivalry with Mary, had managed to seduce Lord Byron. Her liaison resulted in a pregnancy. This excursion to Geneva, then, was assumed so as to acquaint Byron first-hand with the necessity of providing for his future child.
Although Byron refused to meet with Claire, he readily gave assurance for this provision, and during the several months the party remained at Geneva, he and Shelley became close friends. During the summer of 1816, while Byron finished Childe Harold's Pilgrimage, Canto 3, Mary set to work on Frankenstein. Shelley wrote surprisingly little, but in Byron's company seems to have discovered his own distinctive stylistic voice, which can be readily discerned in the two poems he then composed, the "Hymn to Intellectual Beauty" and "Mont Blanc." On 29 August, the day before Mary's nineteenth birthday, the Shelley party left for home, carrying the manuscript of Byron's poem for delivery in London.
In November of 1816, Harriet Shelley commited suicide by drowning herself in the Serpentine, the small river that flows in Hyde Park. The body was not recovered for some time, and when it was found it was determined that Harriet had been pregnant. Shelley learned of this event on 15 December, and plans were immediately made to legitimate his relationship with Mary. On 30 December 1816, Shelley and Mary Godwin were married in St. Mildred's Church in Bread Street, near St. Paul's, the street on which John Milton had been born two centuries earlier.
The fall-out from Harriet's suicide was immediate. Her family, instigated especially by her sister Eliza, sued Shelley in Chancery Court to bar him from custody of his two children by Harriet. On 27 March 1817 the Court, citing especially the notes to Queen Mab, ruled that Shelley was unfit to raise these children. They were ordered placed in foster care, with Shelley required to set aside a sum sufficient for their maintenance. For the heir to a baronetcy and son of a Member of Parliament to be treated in such a manner testifies to the extraordinary level of political reaction to which England had sunk in the wake of the defeat of Napoleon. Shelley saw himself singled out for persecution, and he and Mary began to think of leaving the country.
That spring Mary essentially finished Frankenstein, although it would not be published until the beginning of the following year. A second child, Clara, was born in September. Shelley, meanwhile, through the year had been at work on his long narrative poem, Laon and Cythna; or, The Revolution of the Golden City. His publisher refused to go forth with this original printing, demanding that it be rewritten to remove the implications of incest between the protagonists. This second version was issued early in 1818 as The Revolt of Islam. That March, once again accompanied by Claire (this time also with her year-old child Allegra), the Shelleys, partly out of concern for Shelley's health, partly to avoid the further persecution they feared, left for Italy, which would become the site where Shelley's genius would flourish.
In the slightly more than four years before his death in a boat accident, Shelley published seven further volumes of poetry: Rosalind and Helen (which included "Julian and Maddalo" and "Lines Written among the Euganean Hills") (1819); The Cenci; Prometheus Unbound; with Other Poems (which included "The Cloud" and his "Ode to the West Wind"); and Oedipus Tyrannus; or, Swellfoot the Tyrant, a satirical drama on the trial for adultery of Queen Caroline which was quickly suppressed (1820); Epipsychidion and Adonais: subtitled "An Elegy on the Death of John Keats" (1821); and Hellas (1822). Many other poems were left in notebooks, some (like the "Letter to Maria Gisborne" and "The Witch of Atlas," both dating from 1820, and "The Triumph of Life," left unfinished in 1822, were published among the Posthumous Poems put together by Mary in 1824. Still others (like the satire on Wordsworth, Peter Bell the Third) were held back, only to appear in her full-scale edition of her husband's poetry published in 1839. His numerous prose works, such as the "Defence of Poetry" and his translation of Plato's Symposium were brought out a year later, in 1840.
Shelley drowned in the Mediterranean Sea on 8 July 1822. After his body washed ashore near Viareggio, it was cremated according to the dictates of Italian law. His ashes were buried in the Protestant Cemetery (actually, Cimitero Acattolico or non-Catholic Cemetery) in Rome. In 1854, three years after Mary's death a monument was erected in memory of both the Shelleys.
Shelley's correspondence appears in vols. 8-10 of the Ingpen-Peck edition of Shelley's Complete Works.