Janeway reminisces about her ancestor Shannon O'Donnell, the first of her family's long line of explorers and one who helped build the Millennium Gate on Earth. She revisits the town of Portage Creek on New Year's Eve 1999, as Shannon O'Donnell nears the deadline to convince the town's last holdout, Henry Janeway, to approve a model for the first colony on Mars.

The episode revisits Janeway's first day aboard the U.S.S. Voyager and then fast forwards 500 years beyond it when her ship is destroyed, Captain Braxton of the 29th century Federation Timeship Relativity contacts Seven of Nine to go back in time to solve the mystery of who planted the "temporal disrupter" which ultimately destroyed the U.S.S. Voyager.