A temporary alliance between the crew of the USS Voyager and the Borg Collective against Species 8472, which gave Voyager safe passage through Borg space and brought Seven of Nine aboard.
The Voyager-Borg alliance is the subject of the two-part Voyager story Scorpion. Reaching the edge of Borg territory, the crew discover that the Borg are being beaten by Species 8472, invaders from fluidic space whose cells destroy anything that tries to assimilate them.
The Doctor finds a way to turn Borg nanoprobes into a weapon against the aliens while treating Harry Kim. Kathryn Janeway offers the method to the Collective in exchange for an escort across its space. Chakotay objects and compares the bargain to the fable of the scorpion and the fox. The Borg appoint a drone, Seven of Nine, to speak for them.
Nanoprobe warheads force Species 8472 to retreat. Seven then tries to assimilate Voyager, as Chakotay had feared, and he uses a neural link to distract her while her connection to the hive is cut. The Borg later hold the episode against Voyager, as does Arturis in Hope and Fear.