Bruiser, a mischievous Jack Russell Terrier, wakes up ready for an adventure. After devising a plan to sneak into Mr. David's preschool, Bruiser weasels his way into different classrooms, meeting new friends and causing many mishaps--mishaps that get many of the students in trouble! After seeing the students sitting out during recess, a new friend helps Bruiser realize that he should take responsibility for his actions. Bruiser then decides to make matters better for all.