Books in the Swords of Charlemagne series

Rejoining Mystere in Paris, Douglas and Margaret find that the search for the second sword will not be as easy as they had thought -- Hauteclere is missing, and there is another force competing with them to find it. Mystere believes that the disappearance is unconnected to Caedda, but they must find Hauteclere before the others do, and before Caedda follows them to Paris. But in the midst of their search, Margaret vanishes. In order to save his wife, Douglas must regain his long-forgotten mastery as a Warden, and to do that, he must find Hauteclere.