Complex sentence: The series stars Jim Caviezel as John Reese, a presumed dead former CIA agent who is approached by a mysterious billionaire named Harold Finch (Michael Emerson) to prevent violent crimes before they happen by using an advanced surveillance system dubbed "The Machine".
Split into simpler sentences: The series stars Jim Caviezel as John Reese, a former CIA agent who is presumed dead. He is approached by a mysterious billionaire named Harold Finch (Michael Emerson) who is trying to prevent violent crimes before they happen by using an advanced surveillance system dubbed "The Machine".