A routine test of Worf's new photon torpedo guidance system sends a potentially hazardous torpedo astray into deep space, which Picard and Data set off to recover via shuttlecraft. When they return from their mission, they find that every inhabitant of the ship has somehow mutated into more primitive forms of life, some dangerous, others not. The cause of this condition is a virus which has now infected Picard, leaving him and Data very little time to reverse the plight of the crew.
