Complex sentence: Seth appears and chops her hand off with an axe, causing her to retreat back to her house.the meantime, Creedence deals with Elliot's one remaining friend, Brent, by drowning him in popcorn.
Split into simpler sentences: Seth appears and chops her hand off with an axe, causing her to retreat back to her house. In the meantime, Creedence deals with Elliot's one remaining friend, Brent, by drowning him in popcorn.