Wesley's experiment gets loose in the ship's computer.
The third season opens with Dr. Beverly Crusher back as the ship's chief medical officer, and the Enterprise on its way to observe a rare stellar event with the scientist Dr. Paul Stubbs. Wesley's experiment on nanites, microscopic machines, escapes and begins to spread, getting into the ship's computers. The tiny machines start to evolve.
The crew must decide how to deal with a new form of life that has accidentally been created. The episode raises the question of when a creation becomes a being with rights. It marks a change in the series, with the show settling into a more confident tone and a new look for the uniforms. Data and Geordi are both important in finding a peaceful resolution to the crisis.