Complex sentence: Mavis becomes upset with her grandfather's behavior and while the family argues, Dennis sadly flees the hotel and enters the forest with Winnie in tow, hiding in her treehouse, but they are attacked by Bela, who mistakes Dennis for a human.
Split into simpler sentences: Mavis becomes upset with her grandfather's behavior and while the family argues, Dennis sadly flees the hotel and enters the forest with Winnie in tow, hiding in her treehouse. They are attacked by Bela, who mistakes Dennis for a human.