They are the last two humans on Earth and he's disappeared.
She thought she'd made it crystal clear that they were to stick together at all times, though with her lack of speech and his, well, being a moron, the message may not have gotten through to him as well as she thought it had. Or hell, maybe he just decided to ignore her and wander off regardless. He was created to make bad decisions, after all.
She's woken to find his sleeping bag empty. She doesn't believe that he was attacked by something feral during the night. She's certain that the deepest sleeper would have woken at the commotion he'd make in that case, between the flailing limbs and the screaming bloody murder. His sleeping bag is twisted, of course, but it always is in the morning.
She goes in search of him. For obvious reasons she cannot call out to him, so she listens for his voice. Calling out for her because he's gotten himself lost. Screaming in pain because he's been attacked in the light of day. There is silence, and dread settles into the pit of her stomach.
She wants a portal gun. It would make this easier.
Night is falling by the time she decides to return to camp. Not because she's given up on finding him, but because she thinks that's where he'll head if he can remember his way back. If he's not there, she'll keep searching. She'll search until her legs won't carry her and she falls to the ground, unconscious.
Relief floods her when she sees a figure crouched near their sleeping bags, and though she's been keeping up a steady jog all day, she bursts into a sprint to reach him quicker. He hears her footfalls and turns around. Grins. Stands up. Starts to say something. "There you are, luv! I've been trying to -"
She reaches him then, and smacks him hard across the face.
"Ow! What was that for?!" he cries, rubbing his cheek.
And then she throws her arms around him, squeezing him tightly and burying her face in his chest.
He laughs uncertainly. "I'm getting kinda mixed signals here, luv," he says. Then he throws his arms around her with equal exuberance. "But hey! Hugs. Hugs are great."
She pulls away from him and starts communicating with him in the way they've established. She mimes sleeping, then snaps awake, and points at his empty, tangled sleeping bag. She points at him, glaring, and then makes a general "where?" gesture.
He puts a hand behind his neck. "I figured I'd just...you know, go foraging. On my own, for once. Get us some stuff." He clears his throat. "Be useful," he adds, so quietly she almost doesn't hear him. "Turned out to be a bit more difficult than I'd anticipated," he continues at normal volume. "Got a bit lost. Just a bit, mind. Not even a bit, like a half a bit. And I thought to myself, 'Now what would she do in this situation?' And I decided to stay quiet, and go in the opposite direction of whatever my first impulse was. Landed me right back here! Safe and sound. And I've been trying to start a fire for us. No luck on that front, the matches seem to be malfunctioning."
She looks down to see he's burnt through half of their box of matches. A weary weight settles onto her. She looks up at him and whaps him lightly across the chest. She points to herself and then to him.
"Stick together. Yes. Got it," he says dismissively. But she wonders if he really does. She grabs him by the shoulders and shakes him, looking into his eyes imploringly.
"Alright! Yes! It was stupid of me. Moronic, even. Won't happen again, I promise." He holds his hand to his chest in a gesture she taught him. After a moment, she nods.
He smiles, and then suddenly his face splits into a grin. "Oh! But don't think the endeavor was entirely useless, I did manage to find something of interest," he says, his tone steadily growing smug. He whips a worn deck of cards out of his pocket. "Ta-da! Didn't I tell you I've been meaning to learn?"
She can't help but smile.
Together they gather flammable material from the rubble, and he makes an effort to stay within her line of vision. She starts the fire with one of their remaining matches. "That is exactly what I did. Precisely. How the bloody hell are you doing that, luv? It's like magic!" he comments, and she smiles again.
They play a game of cards by firelight that, because she has no voice to teach him any actual games, is completely made up by him, on the spot. An ace of fours is the best hand. Unbeatable.
And despite all the rules he creates in order to ensure his victory, he still somehow manages to lose.