The brother-in-law is alone at home because his wife is away. Although he is a brother-in-law, he is in love with his sister-in-law because she is no less attractive than his sister and is also a stranger, so he cannot control himself in the rain. His wife stopped by the house because she forgot to bring an umbrella. She was soaked. The loud thunderclap rang out, causing her sister to panic and rush to hug him, making him even more determined to commit incest.