Ganino and Stillwell were particular fans of two episodes from the original "" series, "" and "The City on the Edge of Forever", and wanted to combine elements from them for a "Next Generation" episode. They came up with a story involving a team of Vulcans investigating the Guardian of Forever. In the past, the founder of modern Vulcan logic, Surak, is killed, causing massive changes to the timeline. The Romulans and Vulcans joined forces to attack the Federation, Worf is no longer a crewmember on the "Enterprise", and Tasha Yar remains alive. Sarek and the Vulcans by the Guardian are the only people not affected by the timeline change and, in the end, Sarek returns to the past to take Surak's place, restoring the timeline.