The Enterprise is somehow knocked back in time and the ship becomes visible to the folks in the US Air Force. Not wanting to mess up the future, they try to get out of there fast--but not until they accidentally take a pilot prisoner. At first, they don't think this is any big deal (Huh? It sure seemed like one). Then a bit later Spock informs the Captain that the pilot's son plays an important part in space travel history so they MUST return the pilot ASAP--especially since at this point, the pilot hasn't yet sired any kids. So, they realize they must erase the pilot's mind and steal the records of their being spotted (boy, this seemed really easy) so that time would not be affected.<br /><br />This is a decent episode but also one that is easily forgotten. Despite having seen the episode many times, it just never seems to stand out in my mind--sort of like eating white bread. Sure, it's filling but not all that memorable.