Complex sentence: Tim must chase Bill as he sleepwalks, Graeme then finishes the antidote and plans to test it by drinking some of the new improved snooze but falls asleep before being able to drink the antidote.
Split into simpler sentences: Tim must chase Bill as he sleepwalks, while Graeme sets to work on an antidote. Upon finishing it, he plans to test it by drinking some of the new improved snooze but falls asleep before being able to drink the antidote.