Complex sentence: A courier from Western Union arrives minutes later and hands Marty a 70-year-old letter from Doc, who was sent back in time to 1885 by the lightning strike and is now trapped.
Split into simpler sentences: A courier from Western Union arrives minutes later and hands Marty a 70-year-old letter. It is from Doc, who was sent back in time to 1885 after the lightning strike and is now trapped.