Welcome to Litsy!

(1981) The Enterprise is called to the planet Alnath, into a situation involving a mysterious archaeological dig, a Klingon dreadnought in orbit, and a shipful of dead Vulcan scientists. Shortly after arrival, the crew begins acting in out-of-character, impulsive ways. The story's okay, except for bits that haven't aged well (though Kirk and Scotty admiring a junior officer's ass must have already been a little cringey even in 1981, surely)