Moody adolescent Danny Reed (Bobby Driscoll) is unhappy with his life at home. Disgruntled and feeling as if no one understands him, he acts out, getting into fights and causing trouble. Finally, he decides to run away from home. But before he takes off, his grandfather, Joshua (Robert Preston), finds his old diary in the family's attic and gives it to Danny to read. Finding out that his grandfather experienced childhood in a similar manner to himself, Danny cleans up his act.