a husband-and-wife team were in a spaceship, doing a long-term exploration mission, when they found alien life--two small (squirrel-sized) dormant husks, but still exciting. they brought the husks into their ship. one of the husks responded to the change in circumstances and animated, causing some undefined problem and had to be destroyed. the other was in a water bath, and slowly reviving. for some reason they couldn't take it out or just toss it out an airlock, even though...

they knew it would animate and become a xenomorph alien. so they were panicking, trying to figure out what to do, when a strange person suddenly appeared on their ship.

the strange person was a time/space traveler, who had opened up several wormholes from his Earth-based lab. the researcher was in his early 20s, but on their ship he was an old man, because of the time distortion. he knew about the alien problem, and was talking with them about a solution.

he brought both of the couple back to Earth, but while the husband stayed int he lab discussing the problem, the wife went wandering around the neighborhood for undefined reasons, which turned out to be procuring explosives, with which she blew up the lab, hoping to remove the wormhole to their spaceship so they wouldn't have to go back.

the researcher was very upset about paradox and time loops, and sent the husband to check things out, but the wife went home.