Complex sentence: The man who pretends to own the painting then kidnaps Cruchot, but Nicole and her friends knock out the group that kidnapped her father, and the painting is returned to its rightful owner.
Split into simpler sentences: The man who pretends to own the painting then kidnaps Cruchot. Finally, Cruchot's daughter and her friends knock out the group that kidnapped her father, and the painting is returned to its rightful owner.