The Klingon moon Praxis explodes and pollutes their homeworld's ozone layer with deadly radiation. The moons' decimation leaves the Klingons with a remaining life span of 50 earth years and Spock proposes peaceful negotiations between their empire and the Federation. This startling revelation of peace to end almost 70-years of unremitting hostility comes as a shock to both sides. James Kirk is ordered once again to command the Federation Flagship Enterprise and take charge of the situation. Shortly into the mission, the Klingon's Imperial cruiser is attacked and the Chancellor of the High Command is killed. Kirk and McCoy beam aboard to offer assistance but are taken prisoner and charged with murdering the Chancellor. Spock races against time to discover what really happened and save his friends.
