Complex sentence: The story will see Catherine Zeta-Jones play a glamorous journalist sent to report on the Walmington-on-Sea Home Guard platoon before MI5 discovers that there is a German spy in the fictional British town.
Split into simpler sentences: The story will see Catherine Zeta-Jones play a glamorous journalist, whom is sent to report on the Walmington-on-Sea Home Guard platoon. This is all before MI5 discovers that there is a German spy, hiding in the fictional British town.