At the beginning of this episode Voyager encounters a spacecraft carrying Doctor Jetrel, a member of the Hakkonian race. Jetrel asks to see Neelix, but on introduction Neelix refuses to speak to Jetrel. He explains that years ago the Talaxians fought a war against the Hakkonians, and that the war ended when the enemy used a weapon on mass destruction called the Metreon Cascade against Rinax, a Talaxian moon. The Cascade caused some form of chain reaction in the atmosphere, incinerating 300,000 of the inhabitants and inflicting terrible injuries and metreon poisoning on the remainder. Jetrel was the inventor of the Cascade, and Neelix blames him for the terrible damage done by the weapon.
Janeway brings Jetrel on board and he explains that he has been working on the effects of the cascade ever since the war. He has been locating those who were on the moon after the cascade in order to check them for metremia, and believes that Neelix may be affected. Neelix initially refuses to be examined by Jetrel, but eventually relents and allows the examination to take place. Jetrel confirms that Neelix received enough of a metreon dose to cause terminal metremia. Jetrel tells Janeway he may have a way to cure Neelix and the other survivors, but to complete his work he needs a sample from the atmosphere of Rhinax. Voyager sets off towards the Talaxian system, which is apparently fairly close by. Neelix and Jetrel have several confrontations about the lather's role in the war; Jetrel claims that he was not responsible for the use of the Cascade on Rhinax, it was the decision of the military. He says that he has suffered also because of his work - his wife left him, taking the children with her, because she believed that he had become a monster. Neelix tells his own story - after the Cascade he had gone to Rhinax to look for his family. While there he came across what he first thought was some kind of monster - until it spoke and he realized it was a young girl, Palaxia, who had suffered from horrible injuries in the many fires caused by the weapon. Palaxia was taken back to Talax where she slowly withered away and died. Neelix asks Jetrel if he has considered the possibility that he really did become a monster, and Jetrel agrees that when he first saw the Cascade tested he had the same thought. Neelix hopes that he has to live with that knowledge for a long time, but Jetrel says he has metremia himself and will soon be dead.
Later, Neelix suffers from a terrible nightmare in which he sees Kes injured in the same way that Palaxia was, and an image of himself who accuses him of being a coward. Kes finds Neelix hiding in the darkened mess hall and he tells her the truth about the war; he thought it was unjustified, so refused to fight. Neelix believes he is a coward and has carried the guilt ever since. Kes tries to convince him that refusing to fight is itself a form of bravery.
When Voyager arrives at Talax they beam a sample of the cloud into sickbay. Jetrel deactivates the EMH and uses the sample in a machine which grows some kind of life form out of it. After a while Neelix arrives and when he sees the thing he accuses Jetrel of carrying out some kind of bizarre experiment. Jetrel grabs a hypospray and sedates Neelix before leaving sickbay.
When the EMH is reactivated he explains to Janeway what has happened. Tuvok detects Jetrel in the transporter room, and a security team is sent to capture him. When questioned by Janeway Jetrel admits that Neelix never had metremia poisoning - he had lied in order to gain their help. He explains that the Cascade vaporized its victims in a manner not dissimilar to transporter technology, and he believes that it may be possible to re-integrate the fragments to re-create the victims. He has collected DNA samples belonging to many of those who were killed by the Cascade and was trying to use Voyagers transporter to scan the cloud, locate all the cells with that DNA, and bring them back together. Janeway is highly doubtful that it could work, but Neelix begs her to try so she agrees to make the attempt.
Initially the results look promising - a figure begins to form on the transporter pad. However, the material is just too scattered and randomized and the process cannot be completed successfully. Jetrel collapses and is rushed to sickbay.
In the final scene of the episode, Neelix confronts the dying Jetrel in sickbay. In an emotional scene he tells him he has something to say - "I forgive you". Jetrel dies moments after hearing the words.
In my Worst of Trek review of "Threshold" I took a few lines to talk about how each series seems to produce duds which are characteristic to that series only. Now I'm about finished on the Best of Trek, and looking back it's clear that the best episodes thrown up by the four seasons are quite similar to one another. When you look at "The City on the Edge of Forever", "Darmok", "The Visitor", and "Jetrel" you find that not one of them has a villain - in each case the struggle is against fate itself. All of them involve a difficult situation which tests the characters involved, often leading to a tragic death. Since we rarely loose main actors, all of them feature a guest star to do the dying part - although it's Jake Sisko who dies in The Visitor, it's Tony Todd who does the actual dying and the writers preserve the character through the reset ending. But the guest stars are never just throwaway deaths (like the well known Redshirts of TOS) - Edith Keeler, Captain Dathon and Jetrel are all fully fleshed out characters. Even in the case of "The Visitor", we learned a tremendous amount about Jake Sisko's character during the episode itself; very little of his previously defined character is required to make this one work.
"Jetrel" fits into this mode well. Jetrel is initially portrayed as something of a sinister character - we know he is partially responsible for hundreds of thousands of deaths and although he arrives professing good intentions, we know where those lead! Then the episode started having fascinating exchanges between Neelix and Jetrel - the former believing he was confronting a monster out of necessity, while Jetrel maintained that what he did, while not nice, was justified. Yet there was an air of something else underneath that front, something I couldn't quite put my finger on. My read of the situation was that Jetrel was Up To Something and that it was probably Something Nasty. This view took something of a knock with the Doctors admission of guilt to Neelix, in a scene as emotional as any I've seen in Trek or elsewhere.
As we get to the scene where Jetrel created his lab top monster, I became convinced that he was definitely up to no good after all! Then we move to the transporter room, and all is revealed. Jetrel stands revealed, not as a monster but as a man who is desperately trying to make up for the burden he has carried so long. His final failure leads directly to his collapse and death - some burdens are too great to carry for so long seems to be the message. The lack of a happy ending is something which features in three of the four top episodes, and is used well here. Jetrel's death scene could easily have slid into sloppy sentimentality, but instead it is a genuinely touching moment.
Special mention goes to Ethan Phillips. I've always been a fan of Neelix - I don't recall a single scene in which Phillips hasn't been convincing and I like the character even though I'd probably go insane if I had to spend an hour stuck in a lift with him. Voyager has tended to under use him, most especially in the last couple of seasons, but in this episode Phillips demonstrates that this character is capable of being far, far more than the ships resident clown. His acting is flawless throughout, never more so than in that death scene. Neelix, who once displayed the courage to refuse to fight, this time finds the courage to forgive Jetrel when it would have been so much easier to keep right on hating.
Overall then, "Jetrel" displays all the qualities common to these lists of the best of the best. Definitely a classic.