When a newly-developed android developed by Starfleet is destroyed, Lieutenant Commander Data helps investigate the incident and who is responsible. During the course of his search he discovers he is not as unique as he once believed.
During the run of the original Star Trek series many other robots and androids were seen, yet Data is often referred to as the only android in existence during the time of Star Trek: The Next Generation. Immortal Coil explains what happened to those other robots and androids, and how Data fits into their histories. The story references several previously-seen artificial intelligences and characters: