Seven of Nine returns from a survey to find the crew has discovered what they think is a wormhole leading to Earth. A probe detects Starfleet signals containing letters full of good news to the crew. Although sensors detect erratic neutrino levels in the wormhole, Starfleet says the flux is unimportant. Suspicious of everyone's unfettered optimism despite signs the anomaly may not be all it appears to be, Seven accesses Janeway's logs. At first the captain reports that scans determined the wormhole was a deception, but in supplemental logs, Janeway suddenly believes it is real.
When Seven locates an alien vessel in the wormhole not detected by Voyager's sensors, she hails it. The alien, Qatai, warns her that her ship is being deceived, but they are cut off when Janeway routes power from the lab to another system. When Naomi Wildman tells her everyone is acting strangely, Seven realizes they are the only two unaffected by whatever is manipulating the crew. Soon, the crew is ordered by Starfleet to take the Doctor off-line to avoid system interference, and to put Seven in stasis to avoid attracting Borg attention while Voyager passes through the wormhole.
As Chakotay escorts Seven to her alcove, she tricks him and erects a forcefield to contain him. With Naomi's help, she keeps security at bay while she transports to Engineering and stuns Torres with a phaser. After erecting another forcefield, Seven attempts to shut down the impulse drive to keep Voyager from entering the wormhole. However, Janeway transmits a surge to the engineering console that knocks Seven out.
Once they enter the anomaly, the crew is unconscious. When Naomi wakes Seven, the two hail Qatai and convince him to beam aboard. He explains the crew has been a victim of psychogenic manipulation. They are inside a bio-plasmic organism, a beast that consumes starships by telepathically preying on their crews' desires. Qatai has been trying for years to destroy the creature, not always successful at evading its deceptions.
After activating the Doctor's program, Seven informs him that Voyager is being devoured in the digestive chamber of the organism. Realizing that bodies are designed to expel foreign objects, they plan to fire one of Qatai's tetryon-based weapons at a pocket of antimatter released from Voyager's warp core. It creates an unpleasant reaction that causes the beast to expel the two ships through its esophagus. Once Janeway and the others regain consciousness, Voyager resumes its course to the Alpha Quadrant, but Qatai returns to the beast, obsessed with defeating it.