How does Beatrice help avoid trouble with his parents?

In Chapter Ten, Beatrice and Roy take the stolen bike to Roy's house. Determined to help Mullett Fingers, Beatrice and Roy make a plan to tell Roy's mother that they are working on a science project at Beatrice's house. Covered by the lie, they return to the salvage yard to help Mullett Fingers, who has a bad infection from the dog bites.