Complex sentence: Katrien escapes to an adjacent room through an interconnecting door and Simon and his wife make violent love, which Katrien hears through the wall, and she gets upset because they were just about to have sex and he is having sex with his wife.
Split into simpler sentences: Katrien escapes to an adjacent room through an interconnecting door and Simon and his wife make violent love, which Katrien hears through the wall. She gets upset because they were just about to have sex and he is having sex with his wife.