Karai offers an alliance.
"Enemy of My Enemy" was a great episode and good set up for the next episode.
Karai sees the Kraang in action, attacking the Turtles in a laser ship, and tries to get Shredder to help fight off the alien invasion, but he's too consumed with revenge to help. So Karai goes to the Turtles and proposes an alliance with them.
The best part of the episode was the battle with Shredder, with the last one being eleven episodes ago. other good parts include hilarious dialogue and great action scenes with Shredder, Karai, Kraang ant the Turtles.
However, Splinter's teaching of trusting your instincts unless they're wrong is a bit confusing (and that's how we it's good advice). But when the Turtles decided to ambush Shredder, Leonardo wasn't trusting his instincts, he was doing what he thought was right and also he didn't know that Karai was Shredder's daughter. Raphael was kinda right when he said that was no chance Karai would truly join their side. But other than the confusing execution of the episode's moral lesson, I have no real complaints about the episode.
8.5 out of 10