Mouthpiece XIII, Mathilde of Loci (2009), tells the story of the moments preceding the disappearance of a fictional exemplar of memory. In 1582, Mathilde left Loci for China in order to spread the knowledge of a mnemonic technique called the Method of Loci, or Memory Palace. The “Memory Palace” technique assigns items selected for memory to specific locations in an architectural space. The items are easily remembered by revisiting those spaces in the mind, to “see” the items attached there. Her pupils were young nobles, and her success with the Memory Palace, in addition to her own prodigious feats of memory, won her renown. In 1602, having been summoned to the Great Hall, she disappeared. This opera recounts the events that took place within the hall.