Remember the quantum slipstream technology that they pioneered, but abandoned? It was abandoned because of instabilities that threatened the destruction of the ship, despite the fact that it did accelerate them forward somewhat faster than standard warp drive. As the "Timeless" episode ends, we see the technology dismantled for "future use"... but it never returns.
Well, guess what? There is a realization that the technology CAN work, but that they just can't use it for long periods--cut the engines as the instability begins to mount up before dangerous levels are hit. Janeway reasons that it's time for them to start "puddle jumping" with the technology and try making it back to the Alpha quadrant. But not before running into trouble... a couple of side plots could be authored to deal with contingencies that delay progress (jumps into unexpected situations). Overall the pace is quick... you feel the desperation of them really trying to get home urgently, as if time was running out.
What they don't realize is that the "slipstream" technology ends up introducing a timewarp effect. The Voyager crew have no idea that they have not only traveled forward great distances, but also traveled backward in time. How far back?
As the final slipstream jump ends in the Alpha quadrant, Voyager is now in the volatile region where they first traveled when pursuing the Maquis ship. And suddenly two ships come into view--the Maquis and the original Voyager. The crew is mesmerized by this realization. As the instability begins to increase, Janeway realizes they have to get out of there fast and orders Paris to immediately go to warp. And they do JUST in time as the Caretaker displacement wave hits the two ships. In effect, Voyager witnesses its Delta quadrant voyage beginning. Full circle.
They head to the closest Federation starbase... now 7 years older than they were when they originally departed. Part I of the episode ends... in Part II, it's the "reunion" of the Voyager crew with the Federation. The debriefings. The reunions with family. And the beginnings of the struggle for reintegration (especially for Seven, as her Borg heritage is considered suspicious). And of course, the final formal awards ceremony where we segue to a montage of clips of each character (kind of like a flashback), recapping their wonderous adventures. A summary celebration.
