Theme: “the day after the end of the world” or irrevocable changes in a way of life.
Required Element: something that used to be abundant and is now nearly or completely depleted.
Required Element: some kind of conveyance (chronal-challenged time machine or humble butter-making yak with cart).

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So what do we do? Ann’s voice sounded frightened and Tony’s reply was quick and impatient.

There’s nothing we CAN do. The only way we could possibly reverse it would have been for Central pull us back, and try again for an hour earlier, so we could stop that stupid bitch before she sprang into action. If there was still a Central. Which there isn’t.

No need to call her a stupid bitch, Ann said mildly and Tony sprang up and paced.

No? What WOULD you like me to call her? How many times, how bloody many times, was it drummed into us? Do nothing. Observe only. No contact. Do not, repeat do not, change anything in any way? How many times, Ann?

Ann’s mental voice strengthened. You don’t need to do it telepathically, when she can hear. She feels bad enough.

He rounded on her, his whole body radiating rage, and opened his mouth. A guttural grunt emerged—a really good ear might have made out words. Ann heard it as “hab gew tried talkig?” and shrugged.

Mary turned back to face them, her eyes under the heavy brow ridges cold. So they don’t talk. Doesn’t mean they can’t talk. Babies learn. These bodies have vocal chords. We have to keep trying. She added aloud “ee cag do id.”

We wouldn’t have to if you had followed orders, Tony flung at her and she shrugged her heavy Neanderthal shoulders.

You’re the leader. ACT like a leader. Okay, one little mistake, I wiped out the future as we know it. I have said sorry every way I can think. Fact remains, the far past is now our present. We control these bodies. We can survive. We can learn to speak. Or we can sit here hating each other and weeping over the biggest spill of milk in all time until we turn to dust. I want to live.

The biggest experiment in human history – sending three minds back thirty thousand years into Neanderthal hosts, on the most extraordinary research trip ever—boils down to Mary wants to live, Tony was bitter, but there was no real heat in it. She was right. He hated her for what she had done, but that hatred had to dissipate. Life—even if it was just one foot in front of the other—had to go on. He sank back down onto the boulder, his enormous unfamiliar head in powerful horny-palmed hands, to try to think, to plan. Mary was right, he was the leader. Two hours ago, the most brilliant man of his generation. Now a Neanderthal youth, accompanied by an elderly Neanderthal woman and another who was probably his sibling, and facing the biggest challenge of his life.

Two plans. He lifted his head at last. We have to find others—we’ll never survive alone. You two had better do that, they might attack me on sight. And I’ll start working on a message. He looked at the sheer granite face of the rock rising behind them. I’ll carve it into that. Maybe, he smiled bleakly, future scientists will work out how to whisk us back. It will take days. Weeks. If it works, we’ll be straight out of here instantly, so I won’t add the last word unless you’re both here. If it doesn’t . . . well, we start life again. Go.

As they finally left he wearily started the search for a stone he could use as a chisel, and another that would do service as a hammer. If he survived long enough to leave the message, if it worked, what then? Where then? A time machine, perhaps, to come from a crude chisel and chunk of rock? Hope was all that was left.