Prior to Ultima IX, Duncan's dagger, a treasured family heirloom, had been stolen by thieves. Duncun sought help in Moonglow. However, the mage Tydus felt that it would be more amusing to send him on a wild goose chase, and so sent him in the opposite direction to the entrance of the dungeon Deceit.
Upon seeing the Avatar leaving, Duncan accused the Avatar of the theft, but the whole matter was cleared quickly and Duncan apologised, cursing that he shouldn't have trusted Tydus, telling the Avatar who that was. He warned the Avatar to beware of the liars in the city.
Returning the dagger later, Duncan gave a free lesson in the first two-handed weapon technique and for a fee of 2500 gold pieces also taught the second. However, he said that the master of the third technique had died, and his knowledge had been buried with him in an unknown place.