Take a look at the passage again:
O'Neil quietly closed the front door and tiptoed through the living room.
Hoping not to wake his sleeping mother, who would begin a loud and long
lecture on missing curfew.
You chose to connect the participle phrase to the main clause in front, like this:
O'Neil quietly closed the front door and tiptoed through the living
room hoping not to wake his sleeping mother,
who would begin a loud and long lecture on missing curfew.
Unfortunately, you cannot connect these two parts simply by removing the period. Review the rules.
Go back to the sentence to try again.