Plot summary
When an explosion within the dilithium chamber of the Federation starship Enterprise ' s main engineering appears to be the work of sabotage, Starfleet Command dispatches Norah Satie (Jean Simmons), a retired rear admiral from the legal division of its support services section, to lead an investigation to uncover the cause.
Worf (Michael Dorn) discovers that J'Dan (Henry Woronicz), a Klingon exchange officer, had been using modified hypospray syringes to encode information into amino acid sequences for secret transport. J'Dan admits his collaboration with the Romulans but attests that he did not sabotage the chamber. Satie and Captain Jean-Luc Picard (Patrick Stewart) interview crew members who associated with J'Dan, including Dr. Beverly Crusher and medical technician Simon Tarses (Spencer Garrett). Satie's aide Sabin (Bruce French) suspects Tarses of lying when questioned, and Satie orders surveillance on Tarses despite Picard's objection that there is no evidence against him.
Meanwhile, Chief Engineer Geordi La Forge (LeVar Burton) and Lieutenant Commander Data (Brent Spiner) determine that the explosion was caused by simple metal fatigue, not sabotage. Picard considers the matter closed, but Satie intensifies her investigation of Tarses, forcing him to reveal that his grandfather was a Romulan. When Picard attempts to put a stop to the investigation, Satie begins investigating Picard himself, with Admiral Thomas Henry (Earl Billings) from Starfleet Security in attendance.
Satie attempts to cast doubt on Picard's loyalty by citing a number of recent incidents, including Picard's assimilation by the Borg. Picard responds with a quote from Satie's own father, respected jurist Aaron Satie: "With the first link, the chain is forged. The first speech censured, the first thought forbidden, the first freedom denied, chains us all irrevocably." Satie is enraged at him invoking her father and condemns Picard as a traitor. Admiral Henry becomes disgusted with Satie's fanaticism and calls a halt to any additional investigation. After they leave the ship, Picard discusses the incident with Worf, noting that humanity has not advanced as much beyond historical injustices as they would like to believe, and humanity must remain vigilant against fanatics such as Satie to protect their freedom.
Credits
Adapted from Wikipedia contributors, The Drumhead. Paragraphs and formatting adjusted; illustrations, reference markers, block quotations and non-story material omitted.