“Timeless” is episode six of season five of Star Trek: Voyager.
Two people in protective clothes beam down onto a cold and frozen wasteland. They follow a tricorder’s readings to a spot, and contact someone, saying they’re there. A view from above shows, beneath the ice, Voyager.
The two beam inside the frozen ship and are revealed to be Chakotay and Harry. Both older. Harry activates one of the wall consoles and says the power grid has been destroyed and the neural gel packs are frozen solid. Decks 9-14 are now deck 10. It looks like Voyager hit the ice at full impulse. Chakotay wants to know the status of the EMH. Harry is trying, but power is down.
Chakotay heads to the bridge, where there are frozen bodies, and Harry heads to sickbay. On the bridge, Chakotay finds Seven of Nine and contacts someone called Tessa on what looks like the Delta Flyer. He says he’s found her and Seven is beamed off.
Harry activates the Doctor who starts with his normal spiel, drifting off as he sees the state sickbay is in. Harry tells him it’s a long story. They need the Doctor’s mobile emitter; he’s coming with them. The Doctor demands an explanation; Chakotay arrives and says they’re changing history.
Back in the past and B’Elanna is smashing a champagne bottle in engineering in front of what looks like all the crew. Captain Janeway announces the next generation in interstellar propulsion, the quantum slipstream drive – evidently, they have made progress with the technology they encountered in “Hope and Fear”. Time to go home. Janeway says to Chakotay she doesn’t know what Starfleet will say about the mishmash of technology. He thinks they will have no complaints. They may nominate them for the Cochrane Medal of Honour. Janeway will start working on her acceptance speech. Chakotay suggests she thanks the Borg Collective.
Neelix’s contribution to the slipstream drive, which he presents to B’Elanna, is a preserved good luck Talaxian fly. Tuvok tells Neelix he is an unending source of astonishment. Probably not the compliment Neelix took it for. Seven of Nine is staring at her hand. She tells the Doctor her visual processors and motor cortex are malfunctioning. The Doctor starts scanning her. Seven is holding a champagne glass. She’s drunk. The Doctor asks how many she’s had. One. She was trying to perfect her social skills as the Doctor told her to. He thinks she’s doing well. Seven starts thanking him for being a good mentor.
Tom isn’t joining the party and Harry asks why. He thinks they built an Edsel, a disaster waiting for happen. He ran a simulation and it didn’t go well. Tom hasn’t told the captain yet. Harry says they will go to the holodeck and run some simulations. It might be a sensor glitch. On the holodeck, the simulation doesn’t go well. Especially as it wasn’t the first. 23 sims; 23 catastrophes.
They head to tell the others. B’Elanna says it can’t be right and a now-sober Seven asks to look at the results. Chakotay has looked at the findings and think they’re correct. Tuvok suggests cancelling the test. Tom says Harry has got a way; take a shuttle in front of Voyager to calculate the needed data regarding phase variances and then broadcast it back. The benamite crystals they are using for the drive are decaying and it may take years to synthesize more. It looks like it’s a choice of trying it or not trying it at all; no chance for testing. Janeway agrees to look at Harry’s flight plan. Later, she tells Chakotay she wants him on the Delta Flyer with Harry. They are going to take the risk.
In the present, the Doctor is told this was 15 years ago. They are no just outside the Alpha Quadrant. Everyone else is dead; they think the captain tried to make an emergency landing, but the ship was heavily damaged and everyone was killed on impact. They got all the way to Earth; all it took was killing everyone they cared about. Harry is rather bitter and is blaming himself.
Starfleet gave up on the search for Voyager 9 years ago. They are going to prevent the disaster from ever happening. Harry made a miscalculation and now he knows how to fix it. They are going to send the data to Voyager. Through time. Seven of Nine has a cranial implant that allows her to communicate with other drones. Using that they will find out when and where she died. Then communicate using a Borg temporal transmitter. Which they stole. Along with the Delta Flyer.
Starfleet is after them as well – with a Galaxy-class starship captained by TNG‘s Geordi LaForge! – and time is limited. As complicated as what they are trying to do seems, it turns out to be not that easy in practice.