While the Turtles are suffering from 'Turtle Pox', a disease that affects only mutant Turtles, Krang has developed a robotic turtle that he calls Metalhead in an effort to destroy the Ninja Ts. But first, in order to program the robot, Krang needs a 'Brainalyzer' scan of the Turtles. Shredder, Rocksteady and Bebop travel up to the surface and force the Turtles out of hiding by breaking into various business establishments throughout the City. Sure enough, the Turtles arrive at the scene of the crime, allowing Shredder to zap them with the Brainalyzer and making good their escape. The Turtles are confused but relieved to be back at home in their beds. (thetvdb.com)