The traveller is the unnamed player character from Find the Cure!
The traveller lived in the anti-matter universe during the decades following the events of Ground One. They witnessed the Time Plague ravage the population of Earth, and eventually were part of a team that reactivated the Einstein-Rosen bridge, though only the traveller jumped through in time.
Traveling alone to the matter universe, the traveller finds themselves in the New Pelvanida bridge room, near a mop and bucket. After obtaining a vial of stabilized francium from the supply closet, they blow the door open and reach a corridor. From the corridor they use a portion of the mop handle and tape from the receptionist's desk in the lobby to fool the thumbprint scanner locking the infirmary. After reviewing the infirmary's medical texts and discovering the recipe for the cure, the traveller visits the electrician's closet an obtains an Arc Flash suit to protect themself from the turret in the control room. They manage to reactivate the bridge, but due to failure to enact safeguards, the computers warn that the bridge will irreparably meltdown in thirty seconds. Depending on the player's choice, the traveller either returns with the cure to their home universe or chooses to remain in the matter universe.