When Seven of Nine begins experiencing flashbacks involving pursuit by Borg and a large black bird, the Doctor attributes it to post-traumatic stress disorder. He advises her to begin eating real food, something she'll need to get used to now that she's human. But after a few bites, Seven has another vision, and a piece of Borg hardware pops through her skin. Reverting to Borg behavior, she threatens Neelix with assimilation.
Meanwhile, Janeway faces tough negotiations with representatives of the B'omar race for passage through their region. Although the crew is immediately alerted to Seven's odd behavior, they are unable to stop her from leaving the ship. After transporting to a shuttle, she takes the craft into B'omar space.
The Doctor concludes that Seven's dormant Borg nanoprobes have somehow become reactivated. The B'omar refuse to allow Voyager to enter their territory to pursue Seven, but Tuvok and Paris sneak a shuttle past their perimeter grid and track her. When they catch up, Tuvok beams over to her shuttle and a struggle ensues. Seven easily wins and traps the Vulcan behind a force field. From there, he questions her reasons for leaving Voyager. Seven explains that she is responding to a Borg homing beacon. Tuvok points out that there are no Borg ships in the region, but Seven insists he's wrong.
Seven tracks the signal to an alien moon and prepares to beam to the surface. Tuvok asks to accompany her, but Seven expresses concern that he'll be assimilated. Tuvok believes he has no reason to fear that possibility. On the surface, they find an old Federation vessel that was partially assimilated by the Borg almost 20 years ago. It is the Raven, a vessel that belonged to the Hansens — Seven's parents. Some of the Borg-modified equipment was left active, including the beacon that triggered her return. Seven confronts the haunting memories of her assimilation by the Borg at the age of six, but is snapped out of the reverie by an attack from B'omar ships. She and Tuvok barely manage to escape the vessel before the Raven is destroyed. They're beamed up by Paris and safely returned to Voyager.