A necklace that used to belong to Marie Antoinette the last French queen before the French Revolution turns up in the hands of a British collector who decides to present it to Queen Elizabeth. Blake & Mortimer's sworn enemy Olrik about to be tried in Paris manages to escape & steals the precious piece of jewellery in front of their very 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 & Mortimer by tipping off the press about his every move.