The Enterprise-D visits Starbase 179 and takes on some replacement crew as part of an Officer Exchange Program. Picard notes that Starfleet thinks it would be a good idea for someone from the Enterprise to participate as well—and mentions that there is a Klingon vessel, the Pagh, in the area that would agree to take on an exchange officer. Inspired, Riker volunteers to participate because "nobody's ever done it before." He has a slightly rocky start, but manages to develop a camaraderie with most of the crew of the Pagh. Most of the crew, anyway—the overly paranoid Captain Kargan is a different story.
Meanwhile, the exchange officers on the Enterprise are adjusting. The overly-eager Ensign Mendon, a Benzite, irritates Worf with his constant suggestions for improvement and apparent arrogance, and when he discovers a potentially dangerous bacteria on both the hull of the Enterprise and the Pagh, he waits overly long to inform Picard of the discovery. When questioned, he states that it is a Benzite regulation to wait until they have a full analysis and resolution before reporting the problem. Picard informs him that if there is a potential for danger to the ship, he should inform the bridge immediately and continue his analysis. Upon discovering that the bacteria is chewing a hole in the hull, and that the Pagh is even more susceptible, the Enterprise changes course to intercept the Klingon ship to warn them of the potential danger.
Unfortunately, Kargan is convinced that the Enterprise deliberately spread the bacteria to them and orders his crew to attack. Riker continues to uphold his oath of loyalty to the Pagh, but before the order to fire can be given he tricks Kargan into taking the emergency transponder that Worf gave him—and Kargan is promptly beamed onto the Enterprise. Worf stuns Kargan before he can attack the bridge crew, and Riker takes command of the Pagh, and orders a bemused Captain Picard to surrender and repair the Klingon ship. Both ships are repaired, and Riker returns command to Kargan, growling at him and allowing Kargan to punch him to retain his dignity. As Lieutenant Klag helps Riker up, he muses that Riker has handled himself well.
Riker: Thank you, my friend.
As the Enterprise finishes fixing the hole in the Pagh, Riker returns to his ship. Picard congratulates him and tells him to go to sickbay. As Worf escorts them there, Riker notes that the Klingons are a very brave and unique people and that he's glad to have Worf with them on the Enterprise. "Thank you, Commander," Worf says, "and welcome home."
This episode provides examples of:
- Absentee Actor: La Forge and Troi do not appear, in LeVar Burton's first absence from the series.
- Alien Lunch: Before his transfer, Riker indulges in Klingon cuisine, which includes serpent worms called gagh. Later on, in the Klingon mess hall, he discovers that Klingons actually eat their gagh while it's still alive. Despite initial hesitation, he eventually takes the plunge.
- Artistic License Biology: What the hell are subatomic bacteria?
- Chekhov's Gun: The emergency transponder that Worf gives Riker before he leaves for the Pagh. It isn't shown or mentioned again until the climax, when Riker uses it to trick Kargan into beaming off the Pagh.
- Early Installment Weirdness: Although this episode establishes many of the standard concepts for the TNG Klingons, there is one odd moment when Klag tells Riker that, to a Klingon, his career is everything and family is less important. This is very much in contrast to concepts of Klingon family-based honour that would soon be introduced. Also, in the same conversation Riker castigates Klag for refusing to contact his father (due to said father's supposed dishonour), angrily reminding him that "he is your father"... But later on, in "The Icarus Factor" we find out that Riker himself is estranged from his own father, and hasn't seen him in 15 years.
- Fish out of Water: Riker as the only human on a ship full of Klingons, and to a lesser extent, Mendon trying to adjust to Starfleet protocol.
- Heroic BSoD: Mendon goes into one after screwing up in matters of protocol. Wesley helps him snap out of it in time to solve the bacteria problem.
- Identical Stranger: Peculiar example with Mendon the Benzite, who looks identical to Mordock from "Coming of Age" (and is played by the same actor) and is initially mistaken for him by Wesley. He says that all Benzites from the same "geostructure" look identical. Apparently this was a case of Real Life Writes the Plot: the script calls for an exchange officer who's not familiar with Starfleet practices, so they couldn't use Mordock—but they still wanted to use the same actor, because the Benzite head cast was molded to fit a specific individual, and hiring the same guy to play Mendon was cheaper than making a new cast for someone else.
- Idiot Ball: Kargan is convinced that the bacteria is a deliberate attack by the Enterprise. Even when his own crew points out the holes in his logic, he insists that the Enterprise gave them the bacteria simply by scanning them.
- Klingon Promotion: Discussed early on by Worf and Riker—it's expected that if a Klingon captain is too weak or unfit for command, his First Officer will assist in his "retirement." During the climax, Riker uses a Downplayed variant—he doesn't kill Kargan, but tricks him into getting beamed off the Pagh for a while, leaving Riker as the ranking officer.
- Meat Moss: Both ships are infested with a fuzzy, rust-colored bacterial colony that doubles in size every quarter-hour and feeds on the metal of their hulls. Getting rid of it serves as the B-plot of the episode.
- Secret Test of Character:
- Kargan tries to get Riker to betray Starfleet; when Riker refuses, Kargan tells him that if he had, Kargan would have executed him as a traitor on the spot.
- More humorously, Kargan is testing Riker's ability to handle Klingon customs throughout the episode. For example, he has a couple of Klingon women come on to him to see how he reacts. (He passes the test.)
- Talk to the Fist: Riker's response to Klag's challenge. The ensuing Curb-Stomp Battle helps him earn the crew's respect.
- That's an Order!:Riker: Cloaking shields off!
- A Threesome Is Hot: When two Klingon women seem to show interest in Riker, and one of the men suggests that they want to see how well Riker can endure them, he responds, "One or both?" This show of bravado endears him to the Klingons, including the women.