Watch Pretty Little Liars Season 4 Episode 21 Online. Best and Free Online streaming for Pretty Little Liars TV Show. We picked the best sites to stream s04e21. Simply pick a site below and click "Watch Now!" button next to it. Some of the links may be broken, please upvote the working and good links so other users see those links for Pretty Little Liars Season 4 Episode 21 s04e21 at the top of the list.