Complex sentence: After discovering that his son is in the Applegate Mansion, which is about to explode, Tim hitches a ride with Fistergraff as Casper arrives at the mansion and finds Chris, and tries to help him escape.
Split into simpler sentences: After discovering that his son is in the Applegate Mansion, which is about to explode, Tim hitches a ride with Fistergraff. Meanwhile, Casper arrives at the mansion and finds Chris, and tries to help him escape.