On the morning of July 6, 1907, the cleaning woman assigned to Bedford Tower in Dublin Castle arrived at work to find the door to the safe-room standing wide open. The inner security door was closed and bolted, but the keys, which also opened the nearby library, had been left dangling in the lock.

When Sir Arthur Vicars, the Ulster King of Arms charged with protecting the castle’s valuables including the Irish Crown Jewels, learned of this perplexing situation, he brushed it off—not entirely unusual given his generally lax treatment of security. (One legend has it that on a night of particularly enthusiastic drinking, the honorable Ulster King of Arms handed his keys over to his friends. After passing out, he woke up the next morning draped in the country’s most valuable ornaments.)

But that all changed later in the afternoon when Vicars dispatched a messenger to the library to drop some valuables off in the safe housed there. He swung the heavy door open to discover… nothing. The safe had been emptied of the Grandmaster Star and the badge that made up the precious Irish Crown Jewels.