 Ganino and Stillwell 's original pitch for " Yesterday 's Enterprise " featured a team of Vulcan scientists , led by Sarek . They accidentally travel to the past using the Guardian of Forever ( a time portal seen in The Original Series episode " The City on the Edge of Forever " ) and kill Surak , the founder of modern Vulcan logic . When they return to the present , they find that the Vulcans are allied with the Romulans and at war with the Federation . Only Sarek and his Vulcan scientists are unaffected by the change , and so he elects to return to the past and replace Surak , allowing the timeline to be restored . Michael Piller was not happy with this script as he wanted the episode to be more centered on The Next Generation cast ; as such , Sarek and the Guardian were dropped from the story . 
