After defeating their nemesis Shredder, Leonardo has shuffled off to South America to contemplate his feelings on the Ninja Turtle life. In his absence, Michelangelo has become a children's birthday party mascot, Donatello works a tech-support job, and Raphael continues his vigilante work as the metal-clad Nightwatcher. When a powerful businessman (Patrick Stewart) enlists April O'Neil (Sarah Michelle Gellar) to help find the final ancient piece in his puzzle of otherworldly intentions, the Turtles, with help from friend Casey Jones (Chris Evans), find they must put their differences aside and battle the trouble heading toward the city.

"TMNT" (as the opening title refers to the film) takes on the unwelcome job of reintroducing the Turtles with a fresh degree of gravity. It's been quite a long time since the "heroes in a half-shell" were tops of the pops, and I'm sure the production was tempted to grind hard into the retro appeal of the franchise. Writer/director Kevin Munroe ignores the calling, and fashions a bold new path for the Turtles.

Now rendered in computer animation, "TMNT" might not have the expected polish and vivid color of the average Pixar production; but what it lack in sharpness it makes up for in ambiance. The film takes a "Batman" detour, upping the darkness and gritty mood of the city to best observe the humanitarian call of the Turtles. Munroe doesn't go haywire; this is still PG-rated fare for the whole family. But it's immediately noticeable that the broad vibe of earlier incarnations has been toned down severely, while shadows and scuffles have been increased, inching the characters back to their Eastman/Laird origins of the mid-80s.

In fact, Munroe has implemented all sorts of changes to the framework of the film, including starting off the picture with the most iconic enemy already defeated. "TMNT" feels like the second issue of a comic book in the way it pushes the audience into the meat of the story (of course, after some introductory narration by Laurence Fishburne). This is no origin tale, yet, in Munroe's deft script, it's not hard to follow the backstory beats for the Turtle newbies out there. It was a treat to watch "TMNT" consistently thwart my involuntary expectations, taking the Turtles to new emotional directions, but making sure the skateboarding, pizza, and "duuuuuuuude" is still attended to in satisfying ways.

I never thought the word "pathos" would be included in a review for a Turtles film, but here we are. The center of the picture explores the resentful relationship Raphael has with Leonardo; the two Turtles struggling with their communication and confrontation of painful feelings. This leads to one of the best sequences in the film, where the two burn off their anger in a rainstorm fight that best showcases Munroe's directorial style and the textures of the animation. It's a touching subplot, and one that Munroe makes ample room to deal with, trusting the audience will be invested in this brotherly spat. Unfortunately, this does push Michelangelo and Donatello to almost cameo status, which might upset some of the more zealous fans.

While employing a screwy sense of vocal star power (Kevin Smith and Ziyi Zhang also provide voices), the core team of Turtles are given wonderful readings by the actors. They understand the crucial aural values of each character, blending agreeably with the newfound fluidity of movement that CG-animation provides. They also interact wonderfully with the Turtle sensei, Splinter. Sadly, legendary actor Mako ("Conan the Barbarian") passed away during the production, making his wise, enchanting take on Splinter and his fatherly love for his green sons the last performance of his remarkable career.

Taking cues from "Dark Crystal" and "Hellboy" for the finale, "TMNT" morphs into a non-stop action film that will surely delight kiddies who need this sort of mayhem added to their Disneyfied diet every now and again. The conclusion hints at the return of an old enemy for the Turtles to battle, and it's a promise I hope they keep.