The Affair of the Necklace: Blake & Mortimer 7 — Edgar P. Jacobs

A necklace that belonged to Marie Antoinette is to be presented to Queen Elizabeth. Blake and Mortimer's sworn enemy Olrik, about to be tried in Paris, manages to escape and steals the precious necklace out from under their noses during a glittering reception in the French capital. The affair threatens to turn into a full-blown diplomatic incident, especially since Olrik is doing his best to embarrass Blake and Mortimer by tipping off the press about his every move.