P B Shelley is the Devil Incarnate

Maurice, or The Fisher's Cot by Mary Shelley; introduction by Claire Tomalin Viking pounds 9.99

The younger Romantic poets and their households led famously peripatetic lives, racketing round Europe shedding boxes, letters and even children en route. Mary Shelley lost a trunk containing all her juvenilia on one trip; it may yet turn up in some inefficient continental lost luggage office. The story behind the discovery of a previously unknown children's story by Mary Shelley is reminiscent of Henry James's The Aspern Papers, a novella inspired by the scramble for the aged Claire Clairmont's last relics of P B Shelley.

Claire Tomalin outlines the story brilliantly, setting Mary Shelley's unpretentious tale in its fascinating context. It was written in 1820 for the 11-year-old daughter of friends of the Shelleys in Pisa. Lady Mountcashell had once been the pupil of pioneer feminist Mary Wollstonecraft, Mary Shelley's mother. Exiled and in disgrace, having split from her husband the Earl, and with two illegitimate daughters, Laurette and Nerina, Margaret Mountcashell could sympathise with the scandal-dogged atheist poet and his wife.

Laurette, the elder daughter, kept the handwritten story, divided into three sections like a three-volume novel of the day ("a playful touch, intended to please a bookish child", comments Tomalin). It turned up last November, alongside such treasures as first editions of Adonais and Epipsychidion, in the library of the Casa Cini, the ancient palazzo still partially occupied by Margaret Mountcashell's descendants. Amazingly, Laurette's second husband lived on until 1914, and is fondly remembered by the family. The world of the Shelleys suddenly seems very close.

And what of the story? "It is a small work, but touched with the same spirit as the greater ones it stands among," says Tomalin. A fine example of Romantic sentimentality, and elaborately constructed for its brevity, it tells the story of Henry/Maurice, a foundling whose parentage is finally revealed after much misery and loss. It ends happily, yet Tomalin is right to highlight its sadness and ambiguity, and to link it to the Shelleys' unhappy legacy of "lost" and dying children.

There was Allegra, Claire Clairmont's child by Byron, shut up in a convent despite Claire's frantic protests (she was soon to die there, aged five). There was William Shelley, dead of a fever in 1819 in Rome aged three; and toddler Clara who died in Venice in 1818 (Tomalin is gentle about blame, but some critics have lambasted Shelley for dragging his family round Italy at the behest of Lord Byron). And there was - still is - the mystery of the foundling child Elena, registered in Naples as being the child of "Bercy Schelly" and "Maria Gebuin" (Mary's maiden name was Godwin). Mary was definitely not pregnant at that time, so who was the mother? Elena died on 9 June 1820, aged 15 months; Maurice was probably written that August.

It is printed here twice: in one form copy-edited, the other retaining Mary Shelley's original spellings and line-endings. The latter is to be preferred for its wayward charm: "semicercle" and "shud" for "should". There is also a humorous poem written by Margaret Mountcashell, "Twelve Cogent Reasons for Supposing P B Sh-ll-y to be the D-v-l Inc-rn-t-", citing his charity, learning and tolerance as proof of devilish propensities.

The real villain here is Byron, whose callous behaviour to Allegra and Claire is impossible to excuse. "I will read no more of his poetry," wrote Lady Mountcashell in disgust. It is sad to note that Tomalin seems also to have become disenchanted with Shelley himself. "I have seen Mary Shelley emerge slowly from the overshadowing reputation of her poet husband to take her place as one of the key figures of the Romantic movement," she comments with approval. It would be a sad victory for political correctness if the easy-to-read gothic novelist and put-upon wife were to overtake the glorious lyric poet in fame. After all, he wrote "To a Skylark" that summer.