Moving on with the Lay...

Sauron, Gorthaur the Cruel and chief servant of Morgoth, seeing that there were strange tidings abroad, was filled with suspicion and sent many Wolves into the Elven-lands. Therefore, in that time when Lúthien came unto the eaves of Doriath, nigh to the Guarded Plain, she found that Celegorm and Curufin were abroad with their hunting-hounds, the chief of these being Huan of Valinor. Huan it was that espied her fleeting as a shadow beneath the trees. He slept not by day or by night, and no enchantment could deter him, and so coming to Lúthien, he brought her to his lord Celegorm. So great was her sudden beauty revealed in the sunlight of the plain that Celegorm stood aghast and enamoured, but he spoke her fair, and when she revealed her purpose to the lords of the Noldor, they besought her to return with them to Nargothrond where she would find aid and counsel. By no means would they reveal that they knew already of Beren and the Quest, nor that the matter of the Silmarils touched them near as the sons of their Maker.

And thus was Lúthien betrayed by the Sons of Fëanor, for they took her cloak and would not suffer her to pass beyond the gates of Nargothrond, nor to speak with any save the brothers Celegorm and Curufin. Celegorm purposed, therefore, (believing that Beren was lost without hope, or dead) to take Lúthien to wife by force, and thus would the power of the Sons of Fëanor be far advanced, for with Felagund dead they would be the mightiest lords of the Gnomes. They purposed not to pursue the Silmarils yet by force or by craft until all the kingdoms of Beleriand were under their dominion. Orodreth, Felagund's brother, was powerless to withstand them, for the Sons of Fëanor held vast sway in Nargothrond and had a large following. And Celegorm sent messengers into Doriath urging his suit.

But Huan was honest and true, and he grieved at the captivity of Lúthien. And so, coming nightly to her prison door, he would sit and listen to all that she had to tell, for he understood the tongues of all things with voice, but it was permitted for him to speak himself with voice thrice only ere he died. But Huan devised the desperate rudiments of a plan for the succour of Lúthien in her need, and coming to her at night again, he brought her her cloak, and by secret ways they escaped Nargothrond and rode away north.