Spoilers released for the finale
Damn, it's intense.
EPF Agent Bishop appears, as a Utrom (a different breed of Kraang) disguised as a human on Earth. He is however a peaceful alien and seeks out the Turtles for help: the Triceratons will invade the Earth to take out the Kraang.
The two species fought over Dimension X; a classic battle of brains vs. brawns. The Triceratons almost won, until the Kraang unleashed a "Black Hole Generator," which destroyed the Triceraton's home planet. The Triceratons have their own Generator which they bring to New York in the midst of a battle.
Things get so tough that Splinter has to go to the Shredder for help. Shredder agrees to help only for preserving Karai's life (no mention of her whereabouts though).
Shredder kills Splinter with a stab in the heart during their assault on the Triceratons. He doesn't care if the Earth gets destroyed, since now he has won. April attempts a Scanner blast on him.
The Earth is destroyed, the Triceratons celebrate their victory and leave. But before it happens, a ship picks up the Turtles, April and Casey. It is piloted by Honeycutt, an ally of Bishop.
He takes them six months into the past, explaining that the Triceratons took them that long to set up their generator and that they have to get all the machine's components before the Triceratons do. With all the parts they should be able to save Splinter and maybe Karai.
http://forums.thetechnodrome.com/showthread.php?t=53027
This is going to be more brutal and heartrending than Booyakasha Showdown and The Invasion.
07/08/06... 786... the sentinel of Allah has arrived.