What do you want so badly that you can taste it - and can you persuade someone to give it to you? That's the subject of a writing assignment Calvin's fourth-grade teacher, Mr. Purdy, gives the class. Calvin wants a dog! He reads what he's written to his mom to see just how persuasive he can be. No way, Mom says: Stella, their babysitter, might be allergic, and Calvin is too irresponsible to care for a pet.

Luckily, Mom's boyfriend, Ledward, is on Calvin's side. He takes Calvin to a place he calls dog heaven. There Calvin meets the dog of his dreams - Streak. Now Calvin's got to convince Mom he's dog-responsible, because he and Streak belong together!