Season 4 of Ninja Turtles has been an interesting beast; with the Shredder taken out of the equation at the end of season 3, it was only narratively appropriate for the series to go into "down time" as both our heroes and villains regroup following the change in the status quo. We've seen teases of what Bishop, Karai, and Hun have been up to, but all that's about to start tying together starting with Karai finally hunting down the Turtles (sans Leonardo) and Splinter.
The big question of the episode is how did Karai find the Turtles' lair where her adoptive father failed? That's not really answered, and it's a sticking point I would liked to have seen addressed. Considering Karai's short tenure as the Shredder (most of which isn't that remarkable in hindsight), this is probably her biggest achievement. Karai destroys the Turtles' home, and it probably would've come as a much bigger shocker if the same plot hadn't essentially been used in "Bad Day" a few episodes back, albeit as an imagined mental attack. Does it detract from what's going on here? Only in the sense of a weird deja vu that TMNT is borrowing from itself so soon. I like the references to past Turtles' adventures - the breaking of Yoshi's Orb and Mikey's Battle Nexus trophy are losses with meaning because we know how these items were obtained. Less impressive is Karai's VA trying her hardest at a Shredder voice - it feels forced and unnecessary. The Foot Ninja seem tougher now that Karai is leading them, but they still fall into the category of disposable fodder. A good cliffhanger ending keeps anticipation up for the next episode.
Overall if you've been waiting for things to hit the fan with season 4, it all starts here. Don't miss out.