Ken recently relocated from Kansas with his mother. He strikes up a conversation with a girl named Julie, unaware that her boyfriend, Tom, is extremely possessive. Tom is taking karate lessons from Lee, a sensei whose brother was killed by a novice police officer named Billy. Billy now works as the janitor at the school attended by Ken, Julie, and Tom. After Ken is attacked by Tom for speaking to Julie once more, Billy steps in to teach Ken self-defense. This ultimately culminates in a showdown between the students and a confrontation between the senseis.