Complex sentence: The next morning Jack and Marty have breakfast at the bar, when the skinny woman comes sitting next to them and sais she knows who killed Danny Harkness, but she can't tell them who because she's being watched.
Split into simpler sentences: The next morning Jack and Marty have breakfast at the bar, when the skinny woman comes sitting next to them. She sais she knows who killed Danny Harkness, but she can't tell them who, because she's being watched.