After seeing what April's mental powers did to Super Shredder, the Turtle are curious of April's crystal. But after testing it's powers, April becomes an unstoppable mental killing machine. The plot gets predictable near the end though, as the Turtles manage to make April destroy the crystal by making her remember stuff she did with the Turtles in the past. Especially when they mentioned Donnie, which speaking of which, he basically died in this episode. And then came back to life! :)
The fight scenes with Casey Jones and the Foot has to be the one of the best parts of the episode. Not only is it a shock how he was able to defeat Tiger Claw, Fishface and Rahzar on his own, but while avoiding Chrome Domes which are on fire inside a moving truck. If only the rest of the episode were as exciting as that scene. I know dudes shouldn't hit girls, but can they at least make a good fight between the Turtles and the Mental April. Even when the demon was released from the crystal, I was hoping it to be some Freaky Aeon Demon Queen who'd later return in some episode. But no, it's just an ordinary corrupted Aeon.
Overall, the episode has a good plot and it does have a lot of drama and tension, but the only sort of action is when Jones is fighting Shredder's henchmen. Oh yeah, and a bonus .5 points for having a Mutagen Man cameo.
By the way, if you have any TMNT (2012) episode you'd like me to review, just name it on the comments.