Melanie 'Mel' Stryder is one of the only rebel humans left after the invasion of the 'souls', parasitic aliens which take over human bodies, erasing the original occupants. Wanderer is a soul who has lived on eight other planets previously, Mel being her ninth body host. She was inserted under emergency conditions, with the intent of using her to access any information Melanie might have about other free humans. This investigation is headed by an individual identified only by title, as "The Seeker", who pressures Wanderer to produce information, and views her with implied contempt for her failure to do so.