Summary Kim wakes up in an alternate reality in which he is living on Earth and was not assigned to USS Voyager.
In an alternative timeline experienced sometime in 2372 Kim discovers that he was not posted to Voyager and is working in Starfleet designing starships: he has been awarded the Cochrane Medal of Excellence for outstanding advances in warp theory, and is currently involved in designing a prototype runabout called USS Yellowstone. He is also living with Libby in an apartment in San Francisco [#22 Non Sequitur]: at the time of his posting to USS Voyager in the correct reality, Kim is engaged to Libby.
Libby
Kim meets Cosimo who turns out to be an alien who saved him from a shuttlecraft crash by sending him to this alternate reality.
Schematic of the runabout Kim has designed in this alternate reality.
Kim explores his office and gets to learn his situation in the alternate reality and how it differs from the correct one.
Looking at the drawing board he surmises, "Guess I'm pretty good."
He orders the computer to display his service record.
Kim (reading): "'Graduated Starfleet Academy star-date 47918. Requested duty on USS Voyager. Request denied. Requested transfer to Starfleet Engineering Corps. Transfer approved. Starship design specialist. Award the Cochrane Medal of Excellence for Outstanding Advances in Warp Theory.' Computer, access Starfleet's Science Academy database. Have there been any temporal anomalies in the space-time continuum in the last 48 hours?"
Computer: "Negative. No temporal anomalies have been recorded."
Kim: "Computer, has there been any contact with USS Voyager since it was lost in the Badlands?"
Computer: "Information on USS Voyager is classified. Security level clearance 3 or above is required to access files."
Kim: "No problem. It's my ship, or at least I thought it was."
Computer: "Security authorisation accepted. Last contact with USS Voyager prior to its disappearance was on star-date 48307.5."
Kim: "Access Voyager crew manifest. Who was the operations officer on board?"
Computer: "Ensign Daniel Byrd."
Kim knows from knowing Paris in their Voyager life that he can find Tom Paris in Chez Sandrine's on the Marseilles waterfront. It turns out that in this reality Paris would have been on Voyager, as guide into the Badlands, were it not for brawl in Quarls' Bar on Deep Space 9. Kim tells Paris he wants him to help him tp recreate the shuttlecraft accident, but Paris sees it as a ploy to get him, a former Maquis officer, to go into Starfleet headquarters. Kim tells him all he sees is "a loser and a drunk". Paris goes to hit him but Kim wrestles him down onto the pool table.
On his return from Marseilles, Kim is arrested and brought before a tribunal. His conversation with Paris was overheard and reported by an informer. He tries to explain that he is from another reality, but surmises that they think he is a spy. Lt. Lasca tells him that the concrete facts in the case are that he accessed classified files on Voyager and contacted a known Maquis sympathiser (Paris). The tribunal adjourns for further investigation, with Kim having a security anklet put on him, which tracks his movements: if he tries to abscond Security would be alerted and formal charges would be pressed.
Cosimo explains he is there to look after Kim: his people rescued Kim from a shuttlecraft accident at the point where a timestream intersected Kim's route. He does not know how to return Kim to his proper reality and argues against trying: Kim could end up when all life was extinct or not even begun, Kim has a nice life - a good career and a beautiful fiancée. But Kim says he does not belong there, and that this reality is not so good for Danny Byrd or Tom Paris. Cosimo gives him a disc containing the location of the timestream intersection.
The alternate Libby is upset by Kim's insistence that he does not belong there and by his attempt to remove the security anklet put on him by Starfleet. Kim has been in contact with the alternate Tom Paris who also had not gone on board Voyager in 2371.
Kim to Libby: "...So you of all people should know that once I've made up my mind about something, I can't let it go. In some ways, it'd be a lot easier to forget about Voyager, just settle in here, build a life, but that wouldn't be me. You wouldn't be getting the Harry Kim you fell in love with. Does that make any sense? The tampering alarm. Security will be here any second. Better go. I promise you, I'm going to try to get back. It may take awhile, and I may not make it, but I swear I will try."
Kim escapes through the window onto the fire escape. Libby closes the window and blocks the way.
Kim dashes down the fire escape. A pursuer grabs his leg and almost causes him to fall.
The other pursuer grabs Kim's leg but Kim thrusts him away.
Kim is cornered by a Security officer but Paris suddenly appears and knocks the officer down.
Kim and Paris flee from the area. Kim tells him he has the co-ordinates he needs and his prototype runabout is just the thing they need to get them there - they can gain access via his office at Starfleet. Paris produces from his right pocket a site-to-site transporter.
They beam into Kim's office which is in the main complex, on level 6, sub-section 47.
[My animated image shown left is made up of 12 selected screenshots of the beam-in.]
Kim locates USS Yellowstone and neutralises the runabout's security lockouts. They dodge phaser fire from two Security officers and beam out immediately before Security can seize them.
Aboard the USS Yellowstone Paris takes the helm and Kim inputs the co-ordinates of the time-stream into the main computer. Paris responds, "Adjusting course to match. Going to full impulse."
Paris reports that a Nebula class starship is in pursuit. Kim tells him that the defence systems have not yet been completed - it was a prototype. Starfleet will do anything to stop them: they think Kim and Paris are trying to steal this prototype. The pursuers order the runabout Yellowstone to power down their engines or they will open fire; Kim and Paris do not respond; the pursuers close to 5,000 kilometres and open fire. Yellowstone's shields go down to 70 percent then 29 percent. After another hit from the pursuers' phasers, the Yellowstone starts to lose antimatter containment. Kim's attempt to stabilise the field fails and he reports, "We could be looking at a core breach." The pursuers close to 3,000 kilometres.
Kim: "If we can't shake them off, maybe we can slow them down a little. This prototype is equipped with tetrion plasma warp nacelles."
Paris: "So?"
Kim: "Tetrion plasma emits multi-flux gamma radiation. It disrupts subspace."
Paris: "We could vent the warp plasma. The second they hit the plasma cloud their engines would stall. Give us a few seconds' breathing room."
Kim: "Exactly."
Paris: "Unlocking the warp manifold."
Kim: "Venting drive plasma."
It works - the pursuers drop back to one tenth impulse.
The Yellowstone's containment fields are critical. They must hurry. They try to recreate Kim's shuttlecraft accident.
Kim: "I think I was travelling at 140,000 k.p.h."
Paris: "You think?"
Kim: "Look, that was another lifetime. I'm doing the best I can."
Paris: "Increasing speed to 140,000 k.p.h."
Kim: "Now, I also remember running a polaron scan. Scanning beam was running at a radius of half a million kilometres, no wait, a quarter million. Activating polaron scan. That should do it."
They impact the intersection but nothing happens. The pursuing starship is repowering. Kim realises he forgot the emergency transport: that the last thing he remembers hearing is Captain Janeway's voice trying to beam him off the shuttle. He has to beam off the ship. Then the Yellowstone loses antimatter containment; 25 seconds to a core breach. Paris locks onto the time-stream and orders Kim to get on the transport pad. He says the pursuing ship will be there in 30 seconds, but Kim argues they must deal shut down the core breach first otherwise in 15 seconds Paris will be killed.
Paris: "Look, if you're right then things will be changed back to the way they're supposed to be and you'll find me back on Voyager."
Kim: "And if I'm wrong, and this doesn't work, you'll be blown up right here."
Paris pushes Kim onto the transporter pad and beams him off the ship. Then the Yellowstone explodes.
Kim finds himself back aboard the shuttlecraft Drake.
Back aboard Voyager, Kim is pleased to see Paris, who does not understand Kim's behaviour.