A woman, after being involved in a deadly space battle, needs Chakotay's help. There's just one problem: her race is basically The Silence without all the creepiness (but still some): memories of her race can't be held in the minds of others!
This episode provides examples of:
- Big "NO!": Just before Curneth uses the neurolytic emitter on Kellin, she says this.
- Deadpan Snarker: After being informed about Kellin's Action Girl skills, Tuvok recommends she be assigned to Neelix in the Mess Hall, to protect him from irate crewmates. Chakotay calls Tuvok on the fact that he just made a joke.
- Downer Ending: Kellin is made to forget all about Chakotay and Voyager, and chooses to go back to Ramura. Chakotay is compelled to write his memories of her down before he loses them.
- The ending is similar to Star Trek: The Next Generation S5E17 "The Outcast".
- Eminently Enigmatic Race: The crew encounter a race of humanoids who emit a pheromone that makes it impossible for other races to remember them. They also have advanced cloaking technology that keeps them from being detected and computer viruses that wipe out any record of them, so the only way to maintain any record of their existence is with old fashioned paper.
- Knight Templar: The Tracers of Ramura, assigned to hunt down and return those who leave the planet, sans their recent memories. Kellin was one, but she chose to give up the life; this is, unfortunately, reversed by the end.
- Laser-Guided Amnesia: The Ramurans have this as a biological trait: other races cannot remember them after a few hours. You can imagine what kind of difficulty that causes when Kellin reveals she fell in love with Chakotay! Their technology is designed to complement this effect.
- The neurolytic emitter which the Ramurans use, their neuralizer. We see Curneth, a fellow tracer, use it on Kellin, to tragic effect because it's slow-acting instead of instant like the neuralizer.
- Love at First Sight: Kellin claims to have had this towards Chakotay, and seems to be preoccupied with her feelings for him rather than conclusively proving that she was on Voyager.
- No Object Permanence: An alien race called the Ramuran gives off pheromones that interfere with long-term memories. Once a Ramuran leaves another creature's presence, after a few hours the other creature will have completely forgotten about ever meeting the Ramuran.
- Oblivious to Love: Chakotay considers himself to be this, and holds it as the prime reason he can't trust Kellin, because she hammers so hard on the concept of their being in love, but he can't remember that at all. Eventually, though, he gives in.
- Older Is Better: Chakotay chooses to write his memories of Kellin down, with actual (okay, probably replicated) pen and paper, because that can't be erased by a computer virus.
- Protagonist-Centered Morality: The "stowaway" that Kellin came to Voyager to retrieve presumably also had a compelling personal reason for wanting to leave his homeworld—perhaps something even more sympathetic than being in love with someone he's known for a maximum of two weeks—but we never find out what it was, nor does anyone in-universe express any curiosity about this point. Kellin's mind-wipe and return to Ramura is shown as tragic, or at best bittersweet, while the other runaway's fate is a throwaway line about him being happy to return post-mind-wipe—and even that isn't certain, since Fridge Logic raises the question of what Kellin did with him when she decided to turn around and return to Voyager. Did she stop by Ramura first to drop him off—bad enough given that she knew he wanted to leave—or worse?
- Warm Milk Helps You Sleep: Chakotay asks Neelix for something to help him sleep, upon which Neelix lampshades how humans use warm milk. They both find the idea repulsive, however.
- What Is This Thing You Call "Love"?: Seven doesn't understand our weird courtship rituals, why we don't just get to the intimacy, and it can't really be explained to her satisfaction.