Stardate: 51268.4. Voyager comes under attack from a Krenim Temporal Ship that alters the course of evolution by wiping out entire species from the timeline.

Stardate: 51425.4. With most of the crew having abandoned Voyager and only a skeleton crew remaining, the crew realize that to stop the Krenim ship from altering history any further, they need allies. They soon realize that the price of history is higher than any of them could have possibly imagined.