S1E21 · The Arsenal of Freedom

The Enterprise has been sent to the Lorenze Cluster to search for the USS Drake after it vanished while surveying the planet Minos, which many years ago became wealthy by selling weapons. When the ship reaches the planet, they are met by a recorded holographic figure (Vincent Schiavelli) advertising "The Arsenal of Freedom", which invites the crew to the surface. Commander William Riker (Jonathan Frakes), Lt. Commander Data (Brent Spiner) and Lieutenant Tasha Yar (Denise Crosby) beam down to the surface to investigate. Riker is met by Captain Rice of the Drake, however Rice acts strangely by interrogating Riker on his ship's armament.

A suspicious Riker decides to test Rice by claiming that the name of his ship is the "Lollipop", which he refers to as "a good ship" in reference to a Shirley Temple song. After Rice asks him about the weapon systems on the Lollipop Riker is able to deduce that the captain is an imposter. Riker continues to feed him false information, after which the "captain" disappears, revealing a floating sentry probe which fires a stasis field around Riker before Data and Yar can destroy it.

The Enterprise cannot beam Riker through the stasis field, so Captain Jean-Luc Picard (Patrick Stewart) and Doctor Beverly Crusher (Gates McFadden) travel to the surface, and Lt. Geordi La Forge (LeVar Burton) is left in command of the Enterprise. As Picard and Crusher attempt to free Riker, another sentry probe appears and fires on them. Picard and Crusher are separated from Data and Yar in the skirmish and fall into a pit, severely injuring Crusher. Meanwhile, Data and Yar discover that the second probe is more powerful than the first and requires their combined power to destroy it.

While Picard tends to Crusher's injuries, Data manages to release Riker from the stasis field. Riker, Yar and Data are again attacked, with this new probe requiring even more phaser power to destroy it. Data deduces that each probe learns from the previous probes' experiences and adapts to become stronger, and that the next probe might be unbeatable.

The Enterprise is fired upon by a cloaked attacker, with each subsequent attack stronger than the last, straining the ship's shields. Chief Engineer Lt. Logan (Vyto Ruginis) goes to the bridge to demand that the Enterprise flee the planet and attempts to take command, as he outranks La Forge, but La Forge refuses, pointing out that Logan lacks the authority to remove him and orders him to return to Engineering. As the attacks continue, La Forge recalls Logan to the bridge and orders a saucer separation, leaving Logan in charge of the saucer and taking command of the star-drive section from the battle bridge to return to Minos.

Still underground, Picard discovers a computer terminal, which he activates, causing a hologram of the salesman to appear and explain that they are witnessing a demonstration of an intelligent weapon system which is able to upgrade itself in response to any enemy threat. Picard surmises that the Minosians and the Drake were destroyed by the weapons. He fails to coerce the hologram into ending the demonstration. Data is able to locate Picard and determines that while the sentries could be set to destroy their own power source, the resulting explosion would probably take out the whole area, including the away team.

Picard finally tells the salesman he will buy the system, causing the salesman to disappear and the probes on the planet to shut down. La Forge uses the planet's atmosphere to reveal the location of the space-borne probe and destroys it. The away team returns to the star-drive section, where Picard allows La Forge to stay in command until they rendezvous with the saucer section, remarking that he left him with the ship intact and would like it returned in the same condition.