Plot summary
The Federation starship Enterprise, under the command of Captain Jean-Luc Picard (Patrick Stewart), approaches the Kavis Alpha binary star system to perform astrophysics research under the guidance of Dr. Paul Stubbs (Ken Jenkins), analyzing the decay of neutronium as a result of a stellar explosion that occurs every 196 years and is due to occur in the next few hours. Stubbs plans to launch a probe, dubbed the Egg, to gather the data, a result of a lifetime's development. Meanwhile, Chief Medical Officer Dr. Crusher (Gates McFadden) has returned to her duties on the Enterprise after a stint at Starfleet Medical.
As the expected time of the stellar explosion nears, the ship malfunctions in odd ways (such as blaring " The Stars and Stripes Forever "), and the issue is traced to the computer core. Acting Ensign Wesley Crusher (Wil Wheaton), who had been working on a project involving microscopic nanites, realizes that he may have inadvertently let two nanites from his experiments loose. The nanites were programmed to find ways to work together and evolve. A scan of the computer core reveals that the nanites have determined a way of replicating themselves and have taken up residence in the computer core.
With the computer controls unreliable, the crew and Stubbs attempt to see if they can remove the nanites from the core. However, Stubbs shoots the core with a burst of gamma radiation, destroying a large number of the nanites. They retaliate by flooding the bridge with nitrogen dioxide, which the crew overrides.
Stubbs is confined to quarters, but the nanites attempt further revenge by shocking him with electricity. Captain Picard prepares to flood the computer core with gamma radiation to remove the nanites completely, but the android Second Officer Commander Data (Brent Spiner) establishes communication with the nanites and allows them to use his body to speak with Picard. Picard realizes that the nanites are self-aware and conscious and took Stubbs' actions as hostile, but they want peace. Picard negotiates a deal to send the nanites to Kavis Alpha IV, designating it as their homeworld. The nanites agree and repair the damage to the computer core before they leave it. Stubbs launches his probe on time and collects numerous volumes of data.
Credits
Adapted from Wikipedia contributors, Evolution (Star Trek: The Next Generation). Paragraphs and formatting adjusted; illustrations, reference markers, block quotations and non-story material omitted.