Paris and Neelix return from a trading colony with a passenger named Arturis. He knows over 4,000 languages, and Janeway agrees to give him passage to the next system. When Arturis studies the encoded message Voyager received from Starfleet before the relay stations were destroyed, he instantly decodes it. Part of the data is a spatial grid with marked coordinates, and Voyager arrives at the designated spot to find a Starfleet vessel waiting there.
Finding no lifesigns on the ship, an away team is sent to secure the U.S.S. Dauntless. On board they find the helm is set for auto-navigation, and it's equipped with a new engine configuration called a quantum slipstream drive. The rest of Starfleet's message says the Dauntless has been sent to bring the crew home. Janeway orders the crew to modify Voyager with the slipstream technology so they can bring it along, but she also senses something isn't right and asks Tuvok to keep an eye on Arturis.
When the Captain reconstructs the last segment of the data block from Starfleet, she finds that they did not send Dauntless. Their efforts only turned up some information about the Delta Quadrant, which Starfleet hopes Voyager can use to find a wormhole. In engineering, Kim discovers alien technology behind one of the bulkheads, confirming that Arturis manufactured the ship. Janeway, Seven of Nine, and Tuvok gather weapons and head to the Dauntless bridge to confront Arturis.
When the security team tries to take Arturis to the brig, he activates the ship's slipstream drive. Kim is able to transport Tuvok and the rest of the team to Voyager, but Janeway and Seven are taken hostage. An angry Arturis explains that his people were fighting against assimilation when Janeway gave the Borg the nanoprobes to fight Species 8472. Those aliens were his homeworld's last hope to defeat the Borg, and he has held a grudge against the Voyager crew ever since. Now, he is taking Janeway and Seven to Borg space to be assimilated.
Seven adapts her Borg technology to break through the forcefield Arturis has erected and turns it off. She and Janeway then attempt to take control of the ship, but their commands are blocked. At the last minute, Voyager arrives and disables the ship's shields. Janeway and Seven are beamed back, and Arturis enters Borg space alone. Unfortunately, the damage caused by using Voyager's warp core modifications to go into slipstream drive was too great, so the crew won't be able to use that technology to get home faster.