Complex sentence: Three months later, Chloe helps free Nate with the help of Nate's old friend Victor Sullivan (Richard McGonagle) and reveals that Flynn is working for Zoran Lazarević (Graham McTavish), a Croatian war criminal, who is after the stone.
Split into simpler sentences: Three months later, Chloe helps free Nate with his friend Victor Sullivan (Richard McGonagle). She reveals that Flynn is working for Zoran Lazarević (Graham McTavish), a Croatian war criminal seeking the stone.