The Borg are suddenly facing Species 8472 and Janeway must make an alliance.
Voyager enters Borg space and finds the Collective under attack from a species that cannot be stopped. The crew is faced with a very difficult decision: join forces with the Borg to fight off a mutual enemy, or find another way through.
The episode is the first part of the season finale and the first time the series features the Borg as a central threat. It introduces Species 8472, an enemy so powerful that even the Borg fear it, and it ends with a cliffhanger that raises the stakes for the entire ship.