The Naked Time

Psi-2000 is a lifeless, frozen world in the final stages of planetary disintegration, an invaluable opportunity for scientific study. But the entire scientific outpost complement is dead, apparently by violence. And soon enough, an odd intoxication of similar nature begins sweeping through Enterprise, threatening all of the crew and even the ship itself, as intoxicated crewmen lose all sense of duty and purpose. Worse, McCoy's investigations reveal no causative agent, limiting his ability to treat those affected.