The Enterprise is investigating the loss of communication with a Federation science vessel and finds the small Oberth-class ship trapped in the plasma streamer of a binary star system.
An away team needs to transport over in order to investigate but the circumstances of the transport requires linking the transporter systems of the two ships, and for the away team members to be beamed over individually. Riker, Worf and Dr. Crusher all beam over without incident before it's Lieutenant Barclay's turn to beam over. He'd been watching over the transports with increasing anxiety and before his transport is energized he cracks and storms out of the transporter room, saying he cannot go through with it.
He goes to a quick counseling session with Troi where he reveals he has a phobia about using the transporter and has always tried to avoid using them as much as possible and this particularly difficult transport was too much to handle. Troi teaches Barclay a Betazoid technique for reducing anxiety which seems to give Barclay the confidence he needs to complete the transport.
Once over on the ship he aids in the investigation on what happened to the small crew of the ship, many of whom are missing. It's not felt they evacuated as all of the ship's support craft are accounted for. The only oddities is the badly burned body of a crewman and shattered containment jar in a superficially explosion-damaged transport chamber.
The away team goes back to the Enterprise to continue the investigation. While inside the transporter beam Barclay appears to see a slug-like creature moving around inside the matter-stream, the creature opens it's mouth and appears to take an attack posture towards Barclay, Barclay raises his arm in defense and is "bitten" in the arm by the creature. When Barclay materializes back on the ship he gives his arm a curious look and seems more agitated.
The investigation on what happened on the other ship raises more mysteries as an autopsy on recovered crewman has odd results with the body's various biological functions turning on and off as the tests are performed.
Analysis of the shattered containment jar suggests part of the plasma from the twin-star system was beamed over and caused the jar to rupture.
None of this fully explains what happened on the ship or where the missing crew members are.
Meanwhile, Barclay gets more and more worried over his physical conditions especially after some odd sensations in his "bitten" arm. He initially believes he has a condition known as "transporter psychosis" (a very rare condition caused during transport oddities that's not been reported in several decades) but checks of the transporter show nothing unusual. Eventually Barclay gets removed from duty as his hypochondria becomes a work distraction.
After another incidence of the energy in his arm manifesting itself Barclay charges into the transporter room and orders Chief O'Brien (an enlisted man, so Barclay's subordinate) to duplicate Barclay's transport conditions. Afterwards, Barclay's is more convinced what he's experiencing is real and alerts the senior staff.
It's eventually determined that there's ionization in Barclay's body caused by his contact with the creatures in the transporter beam. The creatures are found to be living in the plasma of the energy-streamer of the star-system and it's believed they became caught in the other ship's transport system after they beamed aboard a sample and caused the container to rupture. The creatures are of such a peculiar enough biology they're able to evade the transporter's biofilter and other safety systems.
A plan devised to remove the creatures from Barclay as they potentially pose a health risk and put into motion. As Barclay is suspended in transport he gets the notion to grapple one of the creatures and when he re-materializes he comes back with one of the missing crewmen. Security officers are sent into the transporter beam to recover the other missing crewmen who became stuck in the transporter system with the help of the alien lifeforms during a test of plasma streamer and resulting attempts to remove the infection from the officers. The recovered officers are going to be fine, the alien lifeforms returned to the plasma streamer, and Barclay no longer seems to fear the transporter but gains a new phobia as a result.
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A pretty technobabble-heavy episode and to be honest I'm not entirely sure the disappearance and recover of the other ship's crew makes a whole lot of sense. Much of what is said in the episode seems to try and go a long way to suggest the transporter is doing something it cannot do but somehow is due to an unusual set of circumstances. The biggest one being that the missing crewmen were stuck int he biofilters of the ships for several days when, usually, a pattern will degrade if int he transporter for more than a few seconds.
Of course we'll also revisit this notion of staying intact in a transporter for vastly longer than normal here in a couple of episodes, but that episode doesn't go as long of a way for it to make sense (... er... "aliens") and also presents a margin of error to make this use of the transporter an impractical one.
On the other hand, the episode spends a lot of time exploring the notion of the transporter, an interesting story short-cut "invented" during the creation of TOS as a way of getting crew members to alien worlds without having to deal with the narrative and effects-heavy hurdles of making trips to planet surfaces via spacecraft.
It seems to want to give us some answers to wonders on the transporter. In the real-world transporting is speculated as being "possible" but not by physically moving matter from one location to the other (as energy or otherwise) but rather the "original" being broken down at Point A with every detail of his body recorded and that information is transmitted to Point B where a person is reconstructed using local matter supplies.
This, of course, introduces the notion that the person at Point B isn't the original person, there being no real continuity between the two persons. The person at Point B is a perfect copy and may think he safely made the trip but in reality the original was destroyed to get the infromation to make the copy.
This episode more-or-less shows us there's a continuity between the two points and that the person even remains aware and conscious during the trip, the episode even giving us our first "inside look" at being transported. This would mean either the transporter isn't making 100% pure conversions but is a nebulous "middle ground" where the person is "energy enough" to be transmitted without making the complete trip or that even though it's all energy the system is maintaining all of the intricate connections between every, single, bit of a person. Meaning while it's all energy the brain is still functioning and even the eyes, muscles, and everything else is still functioning. The transporter is just "somehow" making it all work to keep the "real person" alive and consistent. Not in-line with what may pan-out in reality but for fiction it works it giving something of a sigh of relief that people aren't willing to *die* so that a copy of them can be somewhere else and continue on with their life.
But, sigh, this episode shows more problems with the character Barclay. The character is entertaining enough and Dwight Schultz does a good job with him but good-god, how is this guy not on medication?!
People suffer from various anxieties, phobias and such today and while not everyone of them gets on medication there's a lot of stigmas and sometimes financial hurdles to go through in order to get the treatment one may need for various conditions.
Barclay lives in a time when medical treatments are free, readilu available and remarkably advanced than our own. Has humanity somehow taken a huge step backward when it comes to mental health? How is Barclay such an anxious, emotional, wreck all of the time? It's almost anachronistic the way he behaves because it's hard to believe a person like this is functioning in such a society, especially given the job he has.
It's interesting that like most present-day hypochondriacs when Barclay thinks he's suffering form something he goes straight to the 24th century equivalent of WebMd in order to self-diagnose himself with an illness/condition.
In this episode the nerd in me enjoys seeing odd little things in just how life and the computer in this time work. During Barclay's medical research he's hearing a list of symptoms when one perks his interest. He then does the 24th-century equivalent of middle-clicking on an in-line link to get more information on THAT. There's also neat little sounds the computer makes as cues to what it is doing as it goes off on the side-search and then returns to finish reading the original search.
The computer nicely dims the lights for Barclay as he lies in bed and even plays some very nice mellow music when Barclay asks for something to help him sleep. But this is the same computer that just minutes earlier wanted Barclay to clarify the temperature of water he ordered and during a stress-reduction when asked for "more birds" in the audio of it goes from a nice collection of birds to a full-blown Birdemic.
Some, some examples of the computer acting properly and nifty, and at the same time issues with it being sort-of the same dumbass that tends to answer questions that weren't even directed at it.
The episode spends some good time with Chief O'Brien, likely back-dooring in some more character development for him as Deep Space Nine prepares to launch and also back-doors in some exposition concerning some more Cardassian/Federation relations and tensions. The Cardassians obviously being huge elements in DS9.
Did the Oberth-class ship in this episode only have a crew of 5? I know those ships are small but 4 strikes me as a pretty tiny crew.
Maybe I'm overly cautious, but testing high-energy plasma that's known to have exploded once already during testing 20-feet away from the warp-core strikes me as a bad idea. Certainly there's labs on the ship for stuff like this?
I find interesting how Data show's concern over Barclay's preoccupation with his condition and reports it Geordi when Barclay is out of the room.
In the "Nitpicker's Guide" the entry for this episode points out how Barclay passes out while wearing a medical-alert armband and the medical teams never seem to come to him. I thought this was an interesting point, but now it seems there's an explanation. I don't know if the Blu-Ray simply had the sound added or if the sound was lost in the days of VHS tapes, Standard-Definition TV and even the DVDs but in the BD of the episode there's a solid "thud" heard from Barclay falling over after he doesn't respond to Geordi's call. So the medical teams don't arrive simply because they've not had time to yet.
I remember when this episode first aired watching it at a friend's house whose father was in the military (Army, IIRC.) As we're sitting there watching and we get to the scene of Troi relieving Barclay of duty, my friend's step-mother asks "Can she do that?" and the father responds with, "Yep. She's the doctor, doesn't matter if it's the captain, If she thinks someone's a risk because of their health she can take them off duty."
Don't know why, but that's always stuck out to me as a memory around this episode.
In the end, an okay episode. I like it, but it just has a few oddities in it that sort of drag it down a bit. I like Barclay and Dwight Schultz but much of the time he just seems really, really out of place.
Next week? Put your boots on.
He clearly thinks Barclay is a fantasist. A dawdling, anxious muppet whose idiotic foibles must be tolerated. Fair play to Frakes. They obviously asked him to play it that way and he does a good job. Barclay, the socially awkward skinny guy who doesn't get girls and Riker, the tall strapping alpha male who has girls pouring out of his quarters 
