Sure thing! At the moment, Isaac is working a case in Tennessee and Sam, Dean, Parker and Cas have run into the darkness for the first time (though Cas is the only one who actually knows what they're up against), and it's corrupting all of them a little bit. We decided earlier to assume that it would bring out the worst in each of them; like, if you concentrate on certain aspects of each character, it would be easy to see them as evil.
You can decide where to jump in!