Complex sentence: Darren was experimenting with Madam Octa, making her climb over Steve, but when his sister, Annie walked in, saw the spider, and screamed, his control over her was lost, and the spider bit Steve.
Split into simpler sentences: Darren was experimenting with Madam Octa, making her climb over Steve, but when his sister, Annie walked in, saw the spider, and screamed. Darren's control over her was lost, and the spider bit Steve.