the enterprise be somehow knock back in time and the ship become visible to the folk in the u air force . not want to mess up the future and they try to get out of there fast but not until they accidentally take a pilot prisoner . at first and they do not think this be any big deal ( huh . it sure seem like one ) . then a bit late spock inform the captain that the pilot son play an important part in space travel history so they must return the pilot asap especially since at this point and the pilot hasn not yet sire any kid . so and they realize they must erase the pilot mind and steal the record of their be spot ( boy and this seem really easy ) so that time would not be affect . this be a decent episode but also one that be easily forget . despite have see the episode many time and it just never seem to stand out in my mind sort of like eat white bread . sure and it fill but not all that memorable .