While studying in the London Library, failing literature research student Roland Michell finds two previously undiscovered letters by Victorian poet Randolph Henry Ash, addressed to an unnamed female poet. There are clues to her identity, however, and Roland concludes that the female poet may have been Christabel LaMotte. Roland decides not to share his dicovery with his research professor (and fellow Ash scholar) James Blackadder, but instead mentions to a colleague that he is interested in Christabel LaMotte. He is directed to Dr Maud Bailey at Lincoln University, an expert on LaMotte and her works. Maud is also a distant relative of LaMotte, being descended from LaMotte’s sister.

Roland shows Maud the letters, and she in turn gives him access to some of her archived material on LaMotte. This includes the journal of Blanche Glover, LaMotte’s housemate and – it is presumed – lover.  Intrigued by the mystery, Maud and Roland travel to the Lincolnshire Wolds to see LaMotte’s grave, and to Seal Court where LaMotte spent her final years. In the nearby countryside, Roland assists a disabled woman who turns out to be Joan Bailey, owner of Seal Court.

Invited to Seal Court for tea, Maud and Roland are shown LaMotte’s old room. Maud remembers a certain poem that leads her to discover a parcel of letters, hidden away in a secret compartment under a dolls’ bed. They are love letters between Randolph Henry Ash and Christabel LaMotte. This newly discovered relationship will change the face of Ash and LaMotte scholarship. It is a hugely important literary discovery.

Meanwhile a rival Ash scholar, the wealthy American Mortimer Cropper, is visiting England on the trail of Ash memorabilia for his well-endowed collection. Roland approaches Beatrice Nest, who is editing the journals of Ash’s wife, Ellen. He reads an extract from the journals, and more information falls into place. Roland and Maud are allowed back to Seal Court to read the letters of LaMotte and Ash. Unable to return home due to heavy snow, they both stay at Seal Court for the night.  They occupy separate bedrooms, but have an awkward encounter in the shared bathroom.

Maud and Roland visit the Richmond house where LaMotte and Blanche Glover lived. More information is discovered in a letter to Ash’s wife. Roland and Maud travel to Yorkshire, where it is known Ash spent time. They discover connections in the work of the two poets that suggest they were in Yorkshire together. Maud and Roland find a jet ornament shop; the salesperson notices Maud's jet brooch and tells her it is Victorian. Maud suspects that it may have belonged to LaMotte. Maud and Roland start to become friends.

In a shift to the Victorian era, we see Ash and LaMotte’s visit to Yorkshire, the nature of their relationship, and LaMotte’s famous poem, ‘The Fairy Melusine’.

Maud reads the suicide letter of LaMotte’s lover, Blanche Glover. Maud's friend, the LaMotte scholar Leonora Stern, arrives with a letter from a Breton relative of LaMotte’s. It reveals that LaMotte spent some time in Brittany, and offers them both the chance to examine a journal that has many mentions of LaMotte and her activities.

Sir George and Joan Bailey, who are short of money, become interested in the financial value of the LaMotte-Ash letters in their possession.

Maud and Roland travel to Brittany. They read the journal and discover that LaMotte was pregnant, but no one knows what became of the child. Some newly discovered poems suggest it was stillborn.

Cropper is closing in on Maud and Roland and their discovery. Blackadder and Stern give a TV interview together about the LaMotte-Ash letters and the importance of keeping them in Britain. Meanwhile, Roland's abandoned girlfriend Val has become involved with a lawyer, Euan, who George Bailey has hired in the matter of the ownership of the LaMotte-Ash letters. Maud and Roland seem to have quietly become romantically involved.

Returning to England, Maud and Roland are approached by Euan, who reveals that the letters may rightfully belong to Maud. Maud is then contacted by Beatrice Nest, who has overheard Mortimer Cropper insinuating that he intends to dig up Ash’s grave, in order to retrieve certain documents buried with him.

Back in the Victorian era, Ash is dying, and LaMotte has written a final letter to him, revealing crucial secrets. Ellen Ash declines to read it or pass it on, for fear of opening old wounds. She lets Ash die peacefully.

Roland, Maud, Leonora Stern, James Blackadder, Val and Euan gather at Beatrice Nest’s house to formulate a plan to thwart Cropper’s intended grave robbery. They follow Cropper to the village where Ash is buried, and spy on his preparations. As Cropper digs up the grave in the dead of night, the Great Storm of 1987 strikes. The watchers pounce on Cropper and his grave goods. They all return to Cropper's hotel and – suddenly amicable in their shared curiosity – open the box that he has dug up. It contains LaMotte's last letter to Ash.

The letter reveals that LaMotte gave birth to a girl, Ash's daughter, but she gave the baby to her sister to raise as her own. This means that the poets' child was Maud’s great-great-great-grandmother, and that she is the rightful owner of their letters. Maud and Roland decide that their relationship might work after all.

Back in 1868, Ash secretly visits the home of LaMotte’s sister. He meets a little girl, whom he recognises as his daughter, and they talk for a while. The girl gives Ash a lock of her hair. Ash asks her to take a message of forgiveness and understanding to her aunt (mother), Christabel LaMotte. But the girl forgets and the message goes undelivered.