Francis is tense tonight, though with excitement more than anything else, so he jumps at the sounds of Riddick's voice, so absorbed had he been in his book.
When he's home alone he's usually nude, and he's fairly certain that Riddick wouldn't care, but just in case he has on a pair of black boxer briefs, his tattoo completely visible. The tail is done, and the beginnings of colour have been put into the back piece. He can practically taste how close he is to being finished.
So Francis pads towards the door, moving near silently. Or silently to a human's perceptions, anyway. He's not sure yet what Riddick is.