Now this one had a lot of things that were simply too tough to digest.
One, was sending Gavin back really the only way to get rid of the ghost? Couldn't Crowley have brought back Fiona's bones, no matter how deep within the Atlantic the rested? If my memory serves me right, during the whole Mark of Cain saga, Crowley had managed to dig something out of the ocean.
Two, how was Crowley able to pervert Rowena's spell when he hasn't shown any special talent in the charms and spells department so far? To have done that without Rowena's knowledge seems next to impossible. She has more brains than him and the Winchesters (including Mary!) put together.
Three, if Gavin stopped Fiona from turning into a ghost and killing all those teachers, hasn't time and past been tampered with? No one noticed that the dead are back? And the stories of their gruesome deaths disappeared off the internet as well? Seriously?
The only silver lining in this sorry episode is that Lucifer won't be able to use Gavin as a bait to make Crowley do what he wants - unless, of course, he offers to bring Gavin back from the dead. Plus I am glad Mary has finally told Sam and Dean that she has been working with the British Men of Letters .
On the negative side though, getting Gavin killed and using that to settle what they owed to Rowena was definitely a low for the Winchesters. I am very afraid that it is going to turn Crowley against them. A very poor way to repay him for what he did for Castiel. :-( I have no idea why Arthur Ketch is hell-bent on driving a wedge between Mary and her sons but I hope the Winchesters see through that soon.
If there is a referendum on this Brexit, I sure am voting an 'Aye' :-)