They decide to present the story that Bob Ewell fell on his own knife and died accidentally during his attack on Jem and Scout Finch. This version of the story is fabricated to protect the person responsible for Bob Ewell's death, Boo Radley.

Rephrase this sentence in 1st grade

They made up a story that Bob Ewell had a accident and fell on his own knife, and that's how he died when he tried to hurt Jem and Scout Finch. They made up this story to keep the person who really caused Bob Ewell's death, Boo Radley, safe.