Enterprise responds to a distress signal from the disputed Valindross system located along the Federation's border with the Tholian Assembly. While conflicts between these two powers are rare - neither race the worlds inhabited by the other tolerable - Valindross is an exception. Although it has no worlds capable of supporting either a Federation or Assembly colony, it was once home to a race of highly advanced beings. Expeditions into the system by both sides have resulting in technological breakthroughs. The potential resources of Valindross brought the two nations to the brink of war as neither side wanted the other to unearth something too advanced. In the end, both side negotiated a "hands off" agreement.
Upon arriving in Valindross, Enterprise encounters an apparently dead Tholian cruiser. Did the Tholians attempt to exploit the resources of Valindross in violation of treaty? After repeated attempts to contact the Tholians have failed, Kirk moves in to investigate and attempt a rescue. Is this a trap? Or perhaps the opening moves in a game tat may ultimately lead to interstellar war?