Lúthien fleeing with Huan
Now Huan devised a plan for the aid of Lúthien; and coming at a time of night he brought her cloak, and for the first time he spoke, giving her counsel. Then he led her by secret ways out of Nargothrond, and they fled north together; and he humbled his pride and suffered her to ride upon him in the fashion of a steed, even as the Orcs did at times upon great wolves. Thus they made great speed, for Huan was swift and tireless.
~The Silmarillion: Of Beren and Lúthien