Margaret was busy stirring chemicals for an "Anti-Bimbo Solution" as Colin polished up a shotgun he got from the latest supply raid. The two had gotten to know eachother better: Margaret was insecure about her appearance in a similar way to Colin, and spent her time fawning over the 11th Doctor (a fictional guy from some TV show.) much like Colin fawned over Samus Aran. They both watched Steven Universe and both of them liked less than healthy things to eat (Margaret was in shape because her mother was a militant fitness nut who'd badger her after even one potato chip.).
However, they had not yet taken their relationship to the... physical level. Jack knew this, sneaking in on them every so often to see if they were getting it on. This time when he came in he looked impatient.
"You two STILL HAVEN'T DONE IT?!" Jack asked.
"Well, yes.... I'm busy concocting a solution, he's on raids, we don't..." Margaret was cut off by Jack.
"Today's the last day to get her knocked up before we go and boot both of you." Jack said to Colin. "An' by boot, we mean toss you into a fenced off part of the yard full of those sluts that'll turn ya into targets for gun practice."
The two froze up in fear.
"You're call. If you don't produce and end up getting shot as sluts, I'll be sure to bury yah, because you have made some contributions, that I'll say." the old man said as he walked out.
They looked at the clock, and saw they had four hours to midnight. They'd either have to hurry up and have some steamy sex or come up with a way out of this. On one had, both of them might not have another chance to get some, and humanity "needed the numbers" as Jack always argued. But on the other hand, neither of them were really parent material: Margaret was always absorbed in her work and disliked the idea of motherhood (to the chargin of her parents), and Colin was simply unprepared for fatherhood.
They spent one of their four hours to midnight thinking it over, and choose to....