An intervention: I scour the shelves of the library, searching for well-worn paperback fiction. I am looking for books that are already full of the traces of readers before: dog-eared pages, torn covers, and pencil markings, etc. I borrow the books, dismantle them completely, then put a page from each book into the paper feed of a photocopier, and copy a single hair onto the page. I reassemble the book and return it to the library. It is important that library patrons will read these books again. There is no way for me to know what their reaction to the hair trace will be, or if it will be noticed at all.