Complex sentence: After becoming small enough to be attacked by his own cat, he winds up accidentally trapped in his basement he goes through the odyssey of battling a voracious spider, his own hunger, and the fear that he may eventually shrink down to nothing.
Split into simpler sentences: After becoming small enough to be attacked by his own cat, he winds up accidentally trapped in his basement. He then goes through the odyssey of battling a voracious spider, his own hunger, and the fear that he may eventually shrink down to nothing.