The alien, Lucifer, didn't just bear an uncanny resemblance, and the name, of the demon of ancient lore, everything about him -- from his wings and horns, to the red skin and his "forked" tail, to his ability to "enthrall" -- screamed that the legends arose from this people who has to have visited Earth in their distant past!
It made Nicole wary -- but not nearly wary enough. Luc made no bones about the fact that he wanted her, nor did he seem to doubt that his ablility to take her and make her his, regardless of the tight security the government held him under.