How does Scout end up in the yard in front of the Radley house?

Scout, Jem, and Dill are playing in the street in front their house with an old tire.  They take turns getting inside the tire and rolling down the street.  When it’s Scout’s turn, Jem gives the tire a big push and the tire rolls into the Radley yard and ends up resting against the porch.  Scout is too dizzy to get up and run, so Jem courageously runs into the yard to rescue her from the Radley’s overgrown, weed-filled yard.   They run back home, and Scout remembers that she heard a laugh come from the Radley house when she was stuck in the tire.  This episode sets the scene for how the children feel about the reclusive Boo Radley, but it also gives us, the readers, a clue that perhaps Boo isn’t the spooky character the children think he is.  Boo laughing at the children’s adventures in the tire shows that he is perhaps harmless and enjoys watching the children play.  It is our first look at Boo Radley and foreshadows the continued interest he has in the welfare of Scout and Jem.