Possession: A Romance, by A.S. Byatt, is indeed a romance, but it is also a mystery, a chase, a satire, and both historical and contemporary fiction. All of these elements come together brilliantly in a novel that explores possession in the context of romantic love and in the ethical or non-ethical behavior of biographers.

Roland Michell is an unknown English scholar with a mediocre part-time job as a research assistant. He is completing some research in the London Library when he discovers two unfinished letters written in the hand of the famous Victorian poet, Randolph Henry Ash. They are stuck between the pages of one of Ash's books and have obviously not been found by anyone else. The letters are written to an unknown woman who is not Ash's wife. Roland recklessly decides to slip the letters into his notebook and essentially steals them from the London Library. It is an unethical decision that could cost him his job, but he is obsessed with finding out the identity of the woman in the letters.

Roland does some sleuthing and finds a potential connection between Ash and a minor poet named Christabel LaMotte. He contacts Maud Bailey at Lincoln University, because she is a scholar of Christabel LaMotte and also a distant relative. He travels to Lincoln to tell Maud about his theory, and she initially dismisses it. Finally, Roland shows Maud his stolen letters as proof, and she reluctantly sets off with him to solve the mystery.

Maud and Roland start at Miss LaMotte's gravesite in Lincolnshire. They meet Lady Joan Bailey near the churchyard when Roland saves her from a precarious situation in her wheelchair. Sir George and Lady Joan invite their new acquaintances to Seal Court for tea as a thank you. The two scholars are a little nervous about their invitation, because Sir George has a reputation for threatening professors with his shotgun when they come around asking about Christabel LaMotte. However, their fears seem unjustified. Sir George and Lady Joan are very cordial. The Baileys discover they are indirectly related to Maud, and they find out that Maud studies Christabel LaMotte and Roland is also a scholar. Lady Joan talks Sir George into giving a tour of Christabel's old room in the turret. During the tour, Sir George allows the researchers to take a closer look at Christabel's things, and Maud discovers a packet of letters hidden under the mattress in a doll crib.

The letters turn out to be a nearly complete set of correspondence sent to and from Christabel LaMotte and Randolph Henry Ash. After some deliberation, Sir George decides to allow Maud and Roland to come to Seal Court in the winter and read the letters. Once they do, they realize there must have been a relationship between the two poets.

Maud and Roland follow clues across England and France, hiding their research from colleagues and lying to friends and lovers about their whereabouts. Their own lives begin to parallel the Victorian poets when they find they are falling in love with each other. Eventually, other scholars catch on, and the race for clues launches into full swing. Maud and Roland find out that Christabel and Randolph did have a love affair that resulted in her pregnancy and also the suicide of Christabel's lesbian lover, but they cannot find any trace of what happened to the child.

The story culminates at the gravesite of Randolph Henry Ash. An unscrupulous scholar and a greedy heir team up and attempt in the middle of the night to dig up a box that was buried with the famous poet. They are caught in the act by their colleagues. The event happens in the middle of the Great Storm of 1987, so all parties retreat to a nearby inn, where they are marooned by candlelight to wait out the storm. As a group they open the contents of the box and discover the final piece of the puzzle.

Christabel did bear a child, a girl named Maia Thomasine Bailey. Christabel's sister, Sophie, and her husband raised the child as their own. Christabel attempted to tell Randolph the truth when he was on his death bed, but the letter was never delivered to him. What Christabel never knew was that Randolph met Maia by chance one summer day while walking and realized that she was his daughter.

The final discovery has numerous implications, but most importantly, it means that Maud Bailey is a direct descendent of both Christabel LaMotte and Randolph Henry Ash. Therefore, she will most likely retain possession of the documents. Roland and Maud consummate their relationship that evening, but their professional and personal futures are undecided at the close of the book.