Complex sentence: In 2014, Costner will appear in a new spy movie in the series, as Thomas Harper, a mentor for the series title character and "3 Days to Kill", a thriller in which he plays a secret service agent.
Split into simpler sentences: In 2014, Costner appeared in the spy movie', as Thomas Harper, a mentor for the series title character. He will also star in "3 Days to Kill", a thriller in which he plays a secret service agent.