The Warners have a problem when Sam develops some aggressive behavior with other playground children. A humiliated Kim points the finger at Greg, but Greg laughs it off and thinks Kim should just let Sam grow out of it. Greg changes his tune after he has to suffer the humiliation when Sam chokes another toddler at the park. So it's off to the library to do some research on how to cure the problem. Jimmy intervenes with his usual against-the-book advice by telling Greg what he did when Dominic became violent -- he found a bigger bully kid to knock some sense into him. Only after Greg pictures Older Sam going crazy and attacking a classmate does he put the books down and agree to do it Jimmy's way. With Kim and Christine off to a baby shower, Jimmy finds a guy with a troublemaking two-year-old who's bigger than Sam, and the fight is on. Marvin, the guy, arrives with his hefty son, Todd, just as Billy and Steve drop by Greg's backyard to see the "match" in person. They're not the only ones; Kim and Christine see it in person too since they came home early. Kim stays mad at Greg, even after realizing baby fight club was the cure.