Librarians normally belong to a very peaceful race. Of course they love books, and it is their duty to preserve and protect the books and manuscripts in various ways against moth (+ worms...), rust and thieves. During the Middle Ages books sometime had to be chained to the shelves to protect them from thieves. Some valuable volumes are still kept in such way today, e.g., in Bibliotheca Mediceo-Laurenziana in Florens, Italy—the oldest public library in Europe.
However, there are actually also librarians among the book thieves. Recently, we had a librarian at our Royal Library in Stockholm who stole a number of valuable books. When he was eventually caught (in a trap that was set for him by his colleagues) he committed suicide by blowing up his whole apartment in a gas explosion.
Daniel Gotthilf Moldenhawer, the chief librarian at the Royal Library in Copenhagen 1788-1823, is notorious for his book thefts. During his 35 years as the chief librarian the Royal Library flourished. The number of volumes increased by three times through purchases and valuable donations. Moldenhawer himself donated many valuable manuscripts, letters and printed books to his dear institution, many of which he had acquired illegitimately during his travels, mainly in European countries, and many which came from the libraries of old monasteries. The specialists at home in Denmark kept quiet, although the provenience was no secret to them. Apparently, he was excused to a certain extent because he donated everything to the library. So this librarian's "deep affection" for books and manuscripts became known to the public only 90 years after his death when in 1917 a Danish newspaper headlines read "En Bogtyv som Overbibliotekar" ("A Book Thief as Chief Librarian").
I have now actually discovered that one of these thefts of Moldenhawer is a leaf from lectionary 42. This manuscript is kept in the Library of Escorial (Scorialensis X III 13; see Kurzgefasste Liste). It has not been noted in the Liste that one leaf with Luke 8,20-1, 26-34 is missing from the MS in Escorial. That leaf is now in the Royal Library in Copenhagen. If I were the chief librarian in Escorial I would demand back this leaf.
Any more stories of manuscript thieves?