“Unforgettable” is episode twenty-two of season four of Star Trek: Voyager.
Harry is long-windedly telling Tom and Chakotay that thanks to some modifications Seven of Nine did to the Bussard collectors Harry can’t tell how full they are until he aligns his sensors with Seven’s. Chakotay thinks he should have just led with that and that next time he should work closer with Seven. Which Tom makes a comment about just before the ship shakes. According to Tuvok, there are proton surges just outside the ship, but there’s nothing there. The captain contacts astrometrics and Seven of Nine says it’s close range weapons fire, suggesting two cloaked ships engaged in battle.
Chakotay says there’s a power surge, as if there’s one exploding. Followed by an explosion on the screen. The other ship is phasing in and out and one lifeform is detected onboard. The ship contacts Voyager and asks Chakotay for help. She doesn’t seem able to hear a response and says if anyone on Voyager can hear her, she needs help, before an explosion cuts the transmission short. Harry is unable to get a lock on the pilot to beam them off, so Chakotay suggests beaming over to stabilise the ship.
Chakotay, Tom and Tuvok beam over but find no lifesigns. The pilot is there, pinned under a bulkhead. Chakotay gets her out and she says she knew he’d come before passing out. Chakotay has them both beamed to sickbay. The captain enters sickbay and asks the Doctor how she’s doing. He isn’t sure; her readings don’t stay in the database. He’s good enough to give a visual inspection, though; nothing life threatening. The woman wakes up and sees the captain. She asks for asylum and says they need to get away. They’ll be coming after her. As to how she knows them; it’s a complicated story. The captain wants Chakotay to stay with her.
When the Doctor leaves the woman, Kellin, tells Chakotay that they’ve met before. He’s sure he would remember. No. He wouldn’t. The memories of her people cannot be held in the memories of others; a pheromone blocks the forming of long-term memory engrams in others. They remember for a few hours, but the memories fade. About a month ago, Kellin spent several weeks on Voyager. She and Chakotay worked closely together. Then she left, knowing that he would forget everything. She returned, because she fell in love with him.
Chakotay explains to the captain, Tuvok, Harry and Tom that Kellin comes from a closed society that doesn’t tolerate people trying to leave. She claims she was on Voyager before; she’s a Tracer, a kind of bounty hunter, who tracks people trying to leave. She found a runaway on Voyager. They need some way of verifying her story. Tom says that their sensors pass right through Kellin’s ship; she could have been shadowing them for a while and learning about them. Captain Janeway thinks that’s unlikely and why the risky battle with the other ship? It would be easier to just ask for asylum. Chakotay wants to see if they can find a trace, even though a computer virus was planted to wipe out all references to Kellin.
Seven if Nine has downloaded Kellin’s logs and they are being compared to Voyager‘s own route. It shows they travelled together for at least two weeks. Neither Tuvok nor Seven are convinced; Kellin says she always liked that about them; their unyielding logic and refreshing scepticism. Chakotay arrives and is told that everything appears legitimate. He asks if Kellin would like something to eat. Yes; she liked Neelix’s cooking. Afterwards, Seven asks Tuvok why Chakotay’s face was flushing. Tuvok does not speculate.
Kellin knows Chakotay’s food preferences and wants to explain how they fell in love – because he returned her feelings. She explains that she got onboard easily, but was detected and confronted by Chakotay in Seven’s cargo bay. The captain didn’t like the idea of a stowaway and, after Kellin explained, asked Tuvok and Chakotay to work with her.
Chakotay has no memories of the relationship they both had, which means that, to him, it never existed. More Tracers appear, wanting Kellin back, but are driven off, though they damage Voyager in the process as they can fire through the shields. Kellin’s people really don’t like others to leave their world. Assuming Kellin is telling the truth, and it looks like she is.