Complex sentence: The burden now lifted from her conscience, she takes a relaxing shower, during which a shadowy figure of an elderly woman quietly enters the bathroom, shoves back the shower curtain and proceeds to stab her repeatedly to death with a large kitchen knife.
Split into simpler sentences: The burden now lifted from her conscience, she takes a relaxing shower. While showering, a shadowy figure of an elderly woman quietly enters the bathroom, shoves back the shower curtain, and proceeds to stab her repeatedly to death with a large kitchen knife.