Complex sentence: Biff Hooper, Phil Cohen, and Chet Morton go with the Hardy Boys on a hike up the Appalachian trail, but things take a turn for the worst when Biff is hurt.
Split into simpler sentences: Biff Hooper, Phil Cohen, and Chet Morton go with the Hardy Boys on a hike up the Appalachian trail. But things take a turn for the worst when Biff is hurt.