It appeared in a cardboard box at the back of an attic, beneath a pile of old magazines: a hardback novel with a faded cover and the library stamp still clearly visible inside. The due date was many years before the person who found it was born.

Rather than keep the book, the finder returned it to the library with a handwritten note apologising on behalf of the person who had borrowed it so many years earlier.

The library staff expected a small curiosity. But they had not imagined what they would find when they opened the book. Between two chapters lay a pressed fern leaf: dry, brownish-green and perfectly intact, with every tiny leaflet in place.

A bookmark from another time

Nobody knows who pressed it or why. Perhaps someone picked it up on a woodland walk and used it to mark a page. Or perhaps it was a keepsake intended to be found again, but never collected. The marked page offers no obvious clues, and staff say that makes the mystery even more fascinating.

No late fee was charged. The book and fern leaf are now displayed together in a glass case at the lending desk, with a sign inviting visitors to imagine their story. Guesses range from a first date to a school science project.

After its long absence, the novel is back in the catalogue. For now, though, it remains exactly where it is.