Having lost his friend and readying to return to his time period, our lead sets up a small shelter away from his local friend and keeps to himself as he sinks into depression while time passes. The time portal eventually appears and the Prof pulls him back on schedule. Our guy left his stuff behind since he lost track of time and had to go in a hurry once he got the warning that the portal was approaching.
Back in his normal time, the Prof debriefs him. The guy glosses over the woman out of depression and tells Prof he lost his stuff in the exit. The Prof anticipated that with the time and location he chose so it’s not a concern. The village is going to experience an extreme cold snap that winter and the entire population dies out, so no matter how badly our lead screwed up in the past, it wouldn’t matter.
Main gets more depressed around the lab and the Prof spends his time monitoring the data and the effects on the time space continuum. Eventually, the Prof declares everything to be cleaned up and time repaired, so they can go back to pick up the supplies.
The story rewinds in time to when the guy left, but now from the woman's POV. As winter starts, she eventually goes to the guy's cabin to check on him and finds him gone. She returns several times but he's never there. She eventually breaks in and rummages through his stuff, taking his modern outfit as a memento and finds it super warm. She takes his logs for her fire and his food stores before stumbling across his emergency nutrition bars, supplies, and journal and realizes that he was not only telling the truth but that he had tech far beyond what she understands and he really was helping her (based on his journal entries and his feelings in them).
She survives the winter with his warmer clothes, the combination of the supplies he gathered in his final days combined with hers, and the nutrition bars.
The Prof and our lead return after the winter has ended, go to his cabin, and then clear out what little they find. Wanting to pay his respects, the pair visit her cabin and see her sprawled out on the bed, thinking she's dead. They’re shocked to find her just sleeping and wrapped in his future outfit to keep warm, both shocked that the other lived. Tearful apologies and hugs are had.
Since she was expected to have died in the storm in the original timeline, the Prof agrees to take her back (played out more as he's scientifically interested rather than anything emotional).
Back in modern times, she's thrilled by modern things and not scared at all (no cliches about being afraid of TV, she actually loves it). They keep her in the lab to slowly acclimate her and give her centuries worth of healthcare to make sure a modern flu doesn’t kill her.
We end on a montage of her looking more modern, the two’s really close friendship, she does better on the Prof's tests than our guy does, and she keeps his old jacket with a shot of her snuggled in it. Awww.