Some surprises, a death, another possible death, some truths being realized, and the introduction of next season's villains....
Well, I have to give Scott credit, he had a plan and stuck with it. Now, I love Scott, but he is not plan guy. That is part of why he needs Stiles, because Stiles can plan. But Scott pulled this one off and he gets serious props for that. Now about that plan:
Remember a few weeks ago when Gerard threatened Scott's mom? Also remember those pills Gerard kept popping? Turns out Gerard has cancer and Scott smelled it on him. Somehow (presumably after talking with the vet), Scott realized that Gerard's plan must be to become a werewolf in order to cure the cancer. So, working with the vet, he replaces Gerard's pills with one filled with mountain ash. When Gerard was at the jail, Scott bumped into him and made the switch then. The mountain ash prevented Gerard from turning. Is he dead? Not sure, but he cannot be in good shape.
So, as I said, very impressed with Scott. I know he had help, but still, the fact that he managed to put the pieces together and come up with a workable plan was impressive. See, this is the thing I really like about Scott. He knows his limits and works with others to compensate for them. His "pack" of Stiles, Alison, and the vet is a good group. Scott is the heart and soul of the group and the others help him out in different ways. Alison (until recently) helped to keep him grounded. Stiles is his friend, the brains of the operation, and his sidekick. The vet has serious amounts knowledge and is a great resource.
See, this support network is of the utmost importance to Scott, which is what made Gerard such an effective enemy. Gerard was able to knock out this support system and keep Scott off balance. By turning Alison into a severe hunter, Gerard took her away from Scott. By kidnapping and beating Stiles, he managed to knock that support away too. Fortunately for Scott, Lydia helped Stiles to do the right thing. When Gerard beat Stiles, he was hurting Scott by removing Stiles from the action. It was only Lydia's talking with Stiles and his yelling at her that got him to snap out of his funk to go help Scott. Ultimately, this is what defeated Gerard's plan. Because Stiles brought Lydia to Jackson, she was able to help him complete his transformation to a werewolf and therefore stop being the Kanima.
Sorry, I know I am rambling a bit. It's just that this part is so important because it helps to understand what I think was the major arc of the season. Last season, Scott was worried about controlling his abilities and learning about what he was. This season, he learned how to be a leader. He is an alpha in his own right; as I've said before. He may not have a wolf pack, but he still has a pack. And I have a feeling that after the events of last night, he may gain a couple new members. Isaac has increasingly been drawn into Scott's orbit over the past few weeks and Mr. Argent is friendlier with Scott. As for Jackson and Lydia, they are the wild cards.
I am not sure whose side Jackson will be on. Theoretically, he should be in Derek's pack, but he was the Kanima first, which may negate that bond. Then there is the fact that when he transformed, he had bright blue eyes. Now, we've seen Alphas with red eyes and Betas with yellow eyes. I do not remember if the Omega had blue eyes or not. If he did, then Jackson is an Omega. If not, then it is possible that the blue eyes signify either that Jackson was the Kanima or that he is free to choose a new pack. He may end up in Scott's orbit or he may go on his own. I don't see him going to Derek, but I could be wrong.
As for Lydia, I suspect that she will follow Jackson's lead in pack choosing. She is new to this and is the only person we have seen so far who was bitten and survived it without being transformed. Does that mean anything beyond her being the one to resurrect Peter? Dunno. But that will be interesting to see.
Part of the reason I don't see Jackson going to Derek is that Derek is the opposite of Scott. He is a lousy leader. He tried to plan, but failed. He doesn't listen to others to compensate for his weaknesses. He does not really have a support system to help him out and consequently has failed miserably. Now that Peter is back and the new pack of Alphas is in town, I wonder what is in store for Derek.
Which brings us to our villains: the Alpha pack. No, this is not the first pack, rather it is a pack of Alphas. That is a genuinely scary thought. Alphas are incredibly powerful and have pretty much been able to mop the floor with anyone (save the Kanima). It took the entire gang to bring down Peter last year. So having a whole pack of the brutes does not bode well for our band of heroes. Really hope they know what they are doing.
Now for some thoughts looking forward:
 Alison has broken up with Scott, but I think they will get together again. He cares about her too much to just give up on her. She needs time to think and process. Glad he is giving it to her.
 Lydia and Jackson are stronger than ever which does not bode well for Stiles' unrequited love. Hope that poor boy catches a break soon, he really deserves it.
 Scott and Stiles are stronger than ever. Glad to see that. Love that the final scene of the season was the two of them just having fun.
 Given that next season is 24 episodes rather than 12, I assume there will be 2 distinct arcs. The first one will be the Alpha pack. Wonder what the second will be.
 How is Scott going to wrap his mother into this? He can't just leave her in ignorance of what he is doing elsewhere. That could be truly interesting.
Until next season!