Complex sentence: Hearing the sirens of approaching police cars outside, the Man with No Name sacrifices himself for Lake's sake by re-arranging the crime scene to look as though he had just committed a botched robbery and killed the bartender.
Split into simpler sentences: Hearing the sirens of approaching police cars outside, the Man with No Name sacrifices himself for Lake's sake by taking the blame for the bartender's murder. He quickly re-arranges the crime scene to look as though he had just attempted a botched robbery and killed the bartender.