Disclaimer: I don't own Contagion.
The next time he sees Ally, he congratulates her. It's a brief acknowledgement that she did something incredibly important, and nothing more. He knows she doesn't want a long, gushing speech.
Sometimes, though, he wants to say more. Not just about the vaccine, not just about how she helped end the epidemic—for now, at least—but about her. About how she stays calm when everything seems wrong, about her intense dedication.
How her eyes light up when she discovers something new.
How he feels lucky that he even works with her.
He wants her to know that she's amazing.
She's still wrapping her head around all the praise when she goes back to work. Part of her is tired of it, part of her marvels at it. But there are only three people whose thanks really matter.
Her father, Ellis Cheever, and David.
In some ways, David is the most important one. He was always there, through all the panic, the mutated strain, the nights when she thought she would give up. He kept her sane.
If she told him, he'd smile, brush it off. Say it was nothing.
But he's important to her.
She needs him to know.