New Delhi, Aug. 18 -- Reacher has always worked best when it keeps things simple: Jack Reacher arrives somewhere, notices what everyone else has overlooked and eventually leaves a trail of broken bones behind him. Season 4 takes that familiar formula and stretches it into a considerably larger conspiracy, with mixed results.

Based on Lee Child's 2009 novel Gone Tomorrow, the fourth season moves Reacher to Philadelphia rather than the book's New York setting. The story begins with a disturbing encounter on a subway train, where a troubled woman named Anna Merrick kills herself in front of Reacher.

What initially appears to be an isolated tragedy soon opens the door to a dangerous conspiracy involving a senator, the CIA and secrets connec...