Board Thread:WARNING ALL USERS False Info\Spoilers/@comment-49.144.128.41-20130730142021/@comment-76.65.14.118-20130730144321

Scott and Stiles found out that the Alphas killed their Druids. I think Stiles and Derek thought that one of their Druids didn't actually die and instead went onto becomming a Darach for revenge. It is now known that Ms. Blake was Paige, so she became a Darach to avenge her death because of the Alphas.

After this happened, they saved Cora. Stiles ended up going with her and between them being at the school and arriving at Stiles house with the Sheriff, that is definitely enough time for him to tell Cora. Stiles could have even told them about their theory in the car.