Master Splinter invites Miyamoto Usagi—and the irresponsible, sloppy Murakami Gennosuke—from their dimension to Earth in the hopes that Usagi can speak to Leonardo about his wayward attitude. When Gen wanders off to explore downtown Manhattan, the Turtles, Usagi and Casey set out to find him. Their search becomes complicated when an assassin, sent after Leonardo by Lord Hebi, follows Gen and Usagi to Earth.