The Enterprise is summoned to transport a dangerous criminal from a starbase prison to a rehabilitation center: brilliant physicist Dr. Georges Mordreaux, accused of promising to send people back in time - then killing them instead. But when Mordreaux escapes, bursts onto the bridge and kills Captain Kirk, Spock must journey back in time to avert disaster - before it occurs. Now there's more at stake than just Kirk's life. Mordreaux's experiments have thrown the entire universe into a deadly time warp. Spock is fighting time...and the universe is closing in on itself with the relentless squeeze of… The Entropy Effect.