After Mouser Robots demolish the Turtles' home, the brothers trace the attack back to Baxter Stockman's factory and rescue April O'Neil. Michelangelo and Raphael butt heads enough that Raphael storms off to the surface alone — where he crosses paths with Casey Jones during a skirmish with the Purple Dragons. A series of escalating threats follows: Foot Tech Ninjas with cloaking devices, genetically mutated enemies, and rising stakes, until all four Turtles reunite to storm Foot Headquarters, confront the brutal Hun, and face the Shredder himself.