LoglineCaptain Pike and his crew welcome a Klingon defector aboard the USS Enterprise, but his presence triggers the revelation of some shocking secrets.
This episode exists because of the stupid Starfleet rule of having traumatized veterans of the war have to interact positively with the supposedly bad-to-good turned war crime enemy. That's a classic example of people acting stupid for "plot" (e.g. we couldn't have this episode without the stupid bit).