One of the most appealing things about Star Trek for a lot of fans, is that at its core it is a program obsessed with telling philosophical questions that truly examine various aspects of human nature. When Gene Roddenberry created it in the late 1960s, he wanted it to be a show filled with futuristic allegory for topical issues such as racism, sexism, and overall diversity. While many aspects of the show have changed from his utopian vision, this element at least rings true even with modern iterations into the franchise.
In a lot of these episodic case studies of the human condition, the show's writers created various mysteries and points of intrigue, most of which were planted early on, then later revisited to explain and conclude the questions raised. One such example is the Borg, who were introduced early on in TNG and then lingered in the background as a threat that the characters had to prepare for; they were expanded upon and fleshed out when they began their invasion. However, some such mysteries are not so lucky, and have been left unanswered or with fairly ambiguous endings, much to the disappointment of fans.
Commander Sela
One such unresolved mystery revolves around the very strange plot surrounding chief of security Lieutenant Tasha Yar (played by Denise Crosby) in TNG. She was one of the primary characters in the early days of the show, and was highly respected on the iconic USS Enterprise D. She had a strong friendship with Dianna Troi, as well as an oddly intimate relationship with Commander Data, which made her death in the episode “Skin of Evil” come as even more of a surprise. She seemed like she was a character who was going to stay, but was rather unceremoniously killed off by the alien Armus.
While Crosby later mentioned that her character was killed off partially due to her own request, as she was reportedly miserable behind the scenes, Yar’s death would not be the end of her appearances in the show. Wanting to return to the show after things improved on set, she returned in the Season 3 episode “Yesterday’s Enterprise” 3 aboard the USS Enterprise C (the Enterprise namesake's predecessor). The ship came through a temporal rift from an alternate timeline where she never died. Not exactly the same Yar, she felt misplaced in the new timeline, and to restore order she decided to return to the Enterprise C, travel back to the past, and restore the timeline. This is the condensed version of the episode, which ends in her presumed death yet again, but her story didn’t end there. Instead of dying, she was captured by Romulans from the past, and later gave birth to a half-human, half-Romulan daughter. This was Sela, who grew up to be commander of a Romanian vessel, played once again by Crosby.
Sela's appearance was marked as a fairly big deal, and in the few episodes she appeared in was heavily suggested to be the next major antagonist of the show. She was cunning and manipulative, as well as acting as a harsh reminder of how Picard failed to protect Yar. The mystery, then, comes into play then after this. Despite such a big deal being made of her character, Sela was never really fleshed out, or made any other appearances. She basically disappeared, with no explanation as to what happened to her, despite both DS9 and the film Nemesis involving the Vulcan counterpart Romulans — something her character would have been perfect for.
The Lost Aliens from “Conspiracy” & “Schisms”
These two species are representative of the many ‘throwaway’ races present within the Star Trek universe. These races are ones created for a single episode, either as friend or foe, that never return in subsequent episodes. Often they are simply used for the single plot, which is normally wrapped up in the end, and then not much is thought of them afterwards. However, this is not the case with the parasite aliens from “Conspiracy,” nor the spooky, space grim reaper style aliens from “Schisms.” Both of these TNG episodes end on either a cliffhanger, or with a massive amount of questions that are never answered.
Starting with “Conspiracy,” the first-season episode deals with exposing a conspiracy within Starfleet. Some senior officers have had their minds taken over and controlled by a brain parasite that has infiltrated the Federation with the aim of conquering it from within. Of course, Picard and his crew being the heroes of legend, they manage to put a stop to the aliens' nefarious ways — but right at the end of the episode, it’s revealed that before their demise, the aliens manage to send out a distress signal to their home world, ushering more of the brain leeches to invade. It was a great cliffhanger that felt ominous in the best way possible, but that was the last anyone heard of them. They were written off as not deserving a follow-up episode, or forgotten about in the mess of writer changes between the first and second season.
The aliens from “Schisms,” meanwhile, are an example of a race of beings that audiences know nothing about. These strange creatures from another dimension kidnap members of the Enterprise crew and perform various leap-related experiments on them. Upon discovery, they simply flee, never to return, leaving the audience with no explanation on who they were, what they wanted, or the nature of their experiments.
Why Was Q Afraid Of Guinan?
Last, but by no means least, comes the question of why the omniscient god-like creature Q is so scared of Guinan, the ship's bartender and old friend of Picard. Story wise, it makes sense they would be at odds, one being a kind and caring friend of the captain, the other being a tricky pain in the behind, seemingly devoting his time to tormenting him in various wacky ways.
Why such an all-powerful being is so afraid of the El-Adrian Guinan, however, is never explained, her character never being shown to have such immense power as the Q continuum. Not only was this fear never addressed, even in her appearance within the second season of Picard, but it was heavily implied that De Lancie’s Q and Guinan herself had history together. Audiences thought that somewhere down the line the writers would explain this, but alas, much like the mysteries above, nothing was to come of it.