(written from a Production point of view)
The Bajoran scientist who used to be Odo's teacher arrives with evidence of others of Odo's kind.
In his bar, Quark is trying to sell pieces of Plegg to a Ferengi customer when Odo walks in and comes up to Quark. The other Ferengi leaves upon hearing Quark's asking price, but Odo takes out latinum as if to buy some of the remains, before informing Quark that he wants to buy parts of Plegg, but that is impossible because Plegg is still alive and well on Khosla II. Quark claims he bought the remains in good faith and demands Odo investigate the fraud against him. As they are discussing this, Dr. Mora Pol enters the bar and calls out to Odo. As Quark starts to talk to Dr. Mora, Odo leaves in disgust, with Dr. Mora walking with him. They head to the Replimat, where Dr. Mora hints that he may have found a clue to Odo's origins.
Benjamin Sisko is sitting on a couch reading a PADD in his quarters when Jake tries to discreetly leave to meet Nog. Sisko asks Jake about his homework, and upon hearing that it is done, tells Jake he can't leave because he should be listening to Klingon opera to appreciate their culture. In frustration, Jake asks his father when was the last time he listened to Klingon opera. Sisko informs Jake that it was when he was his son's age, and then suggests that Jake invite Nog over and they can listen to the Klingon opera together. Jake walks off in frustration as Odo enters. Odo requests the use of a runabout for investigation of a planet in the Gamma Quadrant, where DNA similar to Odo's had been found.
Jadzia joins Odo, Dr. Mora, and a Bajoran scientist named Dr. Weld on the runabout. Dr. Mora encourages Odo to tell Jadzia the story of when he was in the lab, but then repeatedly interrupts Odo to correct him. The four people beam down to the planet, L-S VI, and begin to scan the surrounding area. They come upon a tall artifact. Apparently it was important to its makers, but the lettering on it is unrecognizable. Jadzia suggests taking it back to the station to let the computers there decipher it. As they are engaged in looking at the artifact, Dr. Weld comes across a lifeform which has similar DNA to Odo. The silicate-based creature is placed in a container, and the artifact is transported up to the runabout. But as soon as it leaves the surface of the planet, the ground begins to shake and a toxic gas is released. In seconds only Odo is left standing. He orders the runabout's computer to lock onto their combadges and transport them back on board.
In the infirmary on the station, Dr. Bashir is caring for the two Bajorans and Jadzia Dax, though he will need more time to understand what happened. Odo wasn't affected by the gas as the others were, presumably because he has no respiratory system, so he joins Miles O'Brien in studying the silicate-based creature that was found on the planet. Along the way, Sisko walks with Odo, presuming he is worried about Mora as a son would if his father was ill. Odo appreciates the thought, but informs Sisko that he doesn't see Mora as a father figure.
O'Brien states that the creature keeps changing, and that he's put a level 5 security field on it. It's been frequently reproducing and undergoing a metamorphosis. He observes the artifact they brought back for a second, then leaves.
The crew looks for signs of what has happened, while Odo sets up a scan for the missing lifeform, and the station goes to yellow alert. O'Brien notes that the lifeform might have gone through the ventilation. Dax enters the science lab and Odo leaves to talk to Dr. Mora. There, Mora attempts to leave sickbay to help find the creature, but Odo convinces him to stay.
As O'Brien crawls through the ventilation duct in search of the lifeform with a tricorder, he is informed by Sisko there was a malfunction in the lab's security cameras and a temporary increase in heat. He suggests a lifeform that feeds off the computer's power, but there should have been an increase detected. Then, he hears something, and follows the sound. He comes across a structural breach, and when putting his hand up to touch the structure it breaks, pouring down some kind of liquid. He identifies it as the missing lifeform, and states that it is now dead.
Dr. Bashir studies the lifeform, and determines that it needed more carbon dioxide to survive. As he is in the infirmary, he hears a noise coming from the ceiling. He is unable to find anything, but as he resumes his work a tentacle comes up from behind and grabs him. He struggles, it lets go, then he uses a laser scalpel to cut the creature. The lifeform retreats back through the ceiling vent, and Bashir calls security down to the infirmary, reporting an intruder alert.
After a team arrives, Bashir explains to them what he has seen, but he did not get a good look at the creature. However, he did agree that the room was warm, so Odo suggests looking for RF energy and the same power fluctuations they saw in the lab. Dax finds organic residue traces, giving more analysis to do. Sisko puts the station on red alert and Odo suggests closing the Promenade.
As Odo and Mora walk away from the infirmary, Mora remarks on Odo's handling of his job, talking about the similarities between police work and the scientific method. He's quite proud, like a father recognizing a child following in his footsteps. Odo just says he was doing his job, but also that he hadn't thought of his approach to his work like that.
Odo and Mora arrive at the lab, and Jadzia reports no luck translating the symbols or with the residue. Jadzia starts a cross-tabulation analysis, and while it runs, Mora talks to her about Odo. She says he's private, but invaluable on the station. Mora clearly regrets the bad parting they had previously, and is pleased that Odo is integrating into society. The analysis completes and they find that the lifeform found on the planet and the one that attacked Dr. Bashir in the infirmary don't have enough similarities to be the same lifeform. Dr. Mora has her run a lengthy analysis on the new sample, but he already knows what it is.
Mora goes to Odo's office to tell him he recognizes the organic sample as being from Odo himself.
Dr. Mora confronts Odo with the likelihood that it was Odo himself, during his regeneration period, who trashed the science lab and attacked Dr. Bashir. Odo proposes that the gas from the planet they were on affected him somehow, but Dr. Mora suggests Odo may have been responsible for unsolved crimes in the past. He then says that now that they know the truth, none of the station staff will trust Odo, and advises Odo to return to the scientific center with him, stating he has experience with Odo.
Odo refuses: he says he doesn't trust Mora, which Mora resents. As they are arguing, Odo hits a security panel and starts to change into something else. Dr. Mora flees from security.
Dr. Mora arrives at Ops as the station crew attempt to find out why the power in security has just failed. He explains that Odo is the creature, and that this metamorphosis is probably a reaction to the gas that was encountered on the planet. Dr. Mora volunteers to be bait to attract the creature that was Odo into a trap. Mora waits on the Promenade, along with Sisko, Kira, Bashir, and station security personnel. The creature comes out and into the force field waiting for it. Dr. Mora watches in distress as the creature slams itself into the force field again and again, realizing then how Odo must have felt during his time at the center – a prisoner. Sisko apparently has the same reaction and orders the force field dropped. The creature then morphs back into Odo and falls to the ground. Mora rushes over to him.
Later, in the Infirmary, Odo is back to normal again, and Bashir informs him that the gas has been purged from his system with help from Dr. Mora. Odo apologizes to Dr. Mora for attacking him, and Mora apologizes for not seeing sooner how Odo felt about their early days together. Mora says he would like to be a small part of Odo's life on the station and visit occasionally, and Odo accepts.
"I am merely a businessman. It would take an orator with the skills of the late, great Plegg himself to sing the praises of the late, great Plegg."
- - Quark
"When was the last time you listened to Klingon opera?"
"When I was your age."
"There, you see?"
- - Jake Sisko, explaining to his father Benjamin why studying for a test on Klingon opera is not important
"Humanoid death rituals are an interest of mine."
"Everybody needs a hobby."
- - Odo and Quark
"Doctor Bashir gave you permission to be up and about?"
"Doctor Bashir wouldn't listen to me and hid my clothes so I wouldn't leave. I had to sneak out to my quarters in a hospital gown that wouldn't close in the back."
- - Sisko and Jadzia
"Feel like getting a raktajino before we call it a night?"
"My replicator or yours?"
- - Jadzia and Bashir
"It's a nickname that I barely tolerate."
"It's an expression of affection that you find difficult to accept."
- - Mora and Odo
"I prescribe rest, because it's hard for a doctor to go wrong with that one."
- - Bashir
Story and script
- The idea for this episode came to Jim Trombetta when he realized that if a shapeshifter was suffering from multiple personality disorder, "not only would he go around exhibiting different personalities, but different bodies." (Star Trek: Deep Space Nine Companion)
- Mora Pol was originally to be played by Rene Auberjonois himself, much as Data's creator Noonian Soong was played by Brent Spiner, and as The Doctor's creator Lewis Zimmerman would later be played by Robert Picardo, but this plan was scrapped when it was realized how much time it would take each day to get Auberjonois out of one make-up and into another. Most DS9 episodes were shot in 7 days, but it was estimated that with Auberjonois playing both parts it would take at least 14 to complete the shoot. (Star Trek: Deep Space Nine Companion)
- When telling Odo the story about his father, Sisko seems to imply (without actually saying it) that his father had passed away after becoming ill. Joseph Sisko ultimately made six appearances in the series, his first one taking place almost exactly two years after this episode. Possibly because of the information disclosed in this episode, it is mentioned in the script of "Homefront" that "several years earlier Joseph fought a debilitating battle against a severe illness, barely surviving. He's never gotten back to full strength, but he's determined to live out the rest of his years with gusto". (Star Trek: Deep Space Nine Companion - A Series Guide and Script Library)
- A script for this episode was sold off on the It's A Wrap! sale and auction on eBay. 
- Special effects supervisor Glenn Neufeld wasn't especially pleased with how this episode turned out, primarily due to the fact that he feels the audience sees too much of the 'monster'; "I figured out the way the script was written, by my timing, we'd be looking at the creature for a minute and a half of screen time. Thirty cuts between three and fifteen seconds each, at various times in the show. I was forced to point out that in the movie Alien up to the moment where we really see it, there are only a hundred frames of creature. And do we really want to see our creature all that time? And, of course, the answer was 'Yes'." (Star Trek: Deep Space Nine Companion)
- Dennis McCarthy scored the music for the episode. McCarthy commented: "I treated it like a horror film. An orchestra can give you tremendous horror effects, but it can also sound dated. Adding the synthesizer pushes you into the era that we're in now". (Star Trek: Deep Space Nine Companion)
- Michael Piller commented, "I like this show. It's the closest thing we've ever done to a monster movie, and the hardest part was to keep the secret that Odo was the one who was actually doing it. I had to throw in a bunch of red herrings." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 69)
- David Carson was pleased with this episode. "I enjoyed 'The Alternate'," he remarked. "It had a lot of different colors and interesting stuff in it." 
- Some viewers saw similarities to Forbidden Planet. The authors of Beyond the Final Frontier wrote, "inspiration for Star Trek in the first place, Odo's bestial form strongly resembles the Id monster at the end of that movie."
- James Sloyan made his first of two appearances as Dr. Mora Pol in this episode. He reprised the role in the fifth season episode "The Begotten".
- This episode establishes that normal travel time between Bajor and Deep Space 9 is five hours. However, in DS9: "The Storyteller", Bashir states that the journey from the station to Bajor takes two hours.
- This episode is the last Star Trek episode to be directed by David Carson. He went on to direct Star Trek Generations.
- The appearance of Dr. Mora in this episode justified the claim Odo made in "The Forsaken", when he told Lwaxana Troi that he modeled his hairstyle after his mentor.
- It seems that Dr. Mora was correct when he identified the monolith as a "relic of Odo's people," as an almost identical monolith can be clearly be seen on the Founders' planet in the episode "The Search, Part II".
Video and DVD releases
- UK VHS release (two-episode tapes, CIC Video): Volume 16, 27 June 1994
- As part of the DS9 Season 2 DVD collection
Links and references
- Rene Auberjonois as Constable Odo
- Siddig El Fadil as Doctor Julian Bashir
- Terry Farrell as Lieutenant Jadzia Dax
- Cirroc Lofton as Jake Sisko
- Colm Meaney as Chief Miles O'Brien
- Armin Shimerman as Quark
- Nana Visitor as Major Kira Nerys
- Sam Alejan as Human sciences division officer
- Ivor Bartels as Human operations division officer
- Tracee Lee Cocco as Antican
- Kevin Grevioux as Human security officer
- Sue Henley as civilian
- Randy James as Jones
- David B. Levinson as Broik
- Mark Allen Shepherd as Morn
- Michael Zurich as Bajoran security deputy
- Unknown actor as
ace; Alpha Quadrant; amusement; analysis; asteroid; Bajor; Bajorans; Bajoran Institute of Science; Bajoran science probe; Bajoran sector; Bajoran vessel (docked); Bajoran wormhole; Board of Ministers; break-in; businessman; carbon-based lifeform; carbon dioxide; cellular structure; Changeling; Chief of Security; "chopping up"; computer; confined to quarters; conduit seal; constable; criminal act; cross-tabulation analysis; Danube-class; Deka tea; display case; DNA chain; DNA pattern; energy fields; engineering crew; entrepreneur; expression; family reunion; Federation; Ferengi; Ferengi death ritual; Ferengi Seal of Dismemberment; Friday; Gamma Quadrant; high security prison; holosuite; homework; hospital gown; ice; intruder alert; Khosla II; kill setting; Klingon; Klingon opera; Krokan petri beaker; L-S VI; label; latinum; letter of authenticity; level 5 security field; lifeform; metamorphosis; minute; Nog; nucleotide sequence; O'Brien, Keiko; Odo Junior; orator; per se; Plegg; polarity; Promenade; Quark's; RF energy; raktajino; red alert; replicator; Replimat; Rio Grande, USS; runabout; scientific method; security camera; sentient lifeform; silicate; Sisko, Joseph; strain; strip; stun setting; synchronous orbit; tentacle; tornado; trace element; tricorder; viscosity; volcanic gas; way station; weigh station; yellow alert; zoo
- "The Alternate" at Memory Beta, the wiki for licensed Star Trek works
- "The Alternate" at Wikipedia
- "The Alternate" at StarTrek.com, the official Star Trek website
- "The Alternate" at MissionLogPodcast.com, a Roddenberry Star Trek podcast
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