While attempting to correct the ecological damage wrought by an asteroid impact, the Enterprise-D was visited by a time pod from the 26th century. The pilot, one Professor Berlinghoff Rasmussen, claimed to be a historian conducting research into the Enterprise's role in the Penthara IV situation. He stayed on board the ship for two days, interviewing several of the senior officers and passing around detailed questionnaires. Rasmussen declined all invitations to comment on the success or failure of the Enterprise's efforts on Penthara IV or other present day events.

During the mission, the Enterprise drilled into several large pockets of carbon dioxide on the planets surface in order to boost the greenhouse effect. Unfortunately, the crust around the drill sites became unstable and extensive volcanic activity threw a great deal of dust into the atmosphere, compounding the original problem. It was suggested that the Enterprise could use the navigational deflector to place a charge on the debris in the atmosphere and then use the ships shields to act as a 'lightning rod', drawing the debris out of the atmosphere and into space. Unfortunately, calculations indicated that there was relatively little margin for error in the procedure - and should the procedure fail, there would be a cascade reaction in the atmosphere which would destroy all life on the planet.

Captain Picard again asked Rasmussen for some clue as to the eventual outcome, and was declined. He proceeded with the attempt anyway, and was successful in clearing the debris from the atmosphere.

Subsequently it was learned that Professor Rasmussen had been stealing various items of technology from the Enterprise; Captain Picard ordered Lieutenant Commander Data to accompany the Professor into his time pod in order to establish his guilt or innocence. Once inside, Rasmussen revealed that he was in fact from the 22nd century, where he had killed a genuine time traveller and stolen the time pod. Rasmussen was arrested and placed in the brig, and subsequently sent to a Starbase for trial.

Temporal scanning determined that Rasmussen had indeed vanished without trace from the preferred timeline in the 22nd century. Temporal Investigations therefore allowed him to remain in the present, where he has now been released from his rehabilitation centre and become a unique source of information for historians.