Board Thread:False Info and Speculative Discussion/@comment-4772791-20160123002637/@comment-5285305-20160124021722

My bets are on Mason - especially after his little speech about not wanting to be on the side of the bad guys when he was talking to Corey.

During the finale, the Beast is reported to be running around and attacks the school in the beginning, and its presence isn't mentioned again for the rest of the episode. Mason doesn't show up until the next night when Melissa is taking care of Hayden.

Now let's look at any info given in the past couple two episodes:

Episode 12: "It's not a Chimera." - Theo

Epsiode 13: "The kid underneath, it's just a side effect. It probably doesn't know it turns back to human back during the day." - Theo

It's heavily implied that whoever is the beast is a regular human kid, and so far we have not seen Mason and the Beast interacting with anyone else during the same time of day. Also, he's recieved plenty of development this season, which can make the reveal more shocking / emotional for the audience and the main characters.

With that said, we're only 3 episodes in with this mystery so it might change depending on the information they give. As of right now though, my money is on Mason.