Once he notices her laugh, he can't help not noticing. He isn't sure if it's the first time he heard it, it might just as well be. She seemed to have even less opportunities to laugh than the others – first there was Ed, then Sophia was lost, then Sophia was dead... But right now they are in an abandoned mall and the women are raiding the baby store. Lori isn't supposed to give birth for another three months, but they never know when they will stumble upon a store like this again. Maggie finds a fluffy baby hat, so ridiculously silly that even Daryl can't help but chuckle. Lori tries to persuade Maggie to put it back, while Beth giggles and Carol...
He doesn't know what's so damn special about her laugh. Maybe it's the way her eyes twinkle. Maybe it's the way she looks down when she notices him watching. Maybe it's the way she tries to put on a straight face, but her eyes still betray her. He doesn't know and he quickly looks away so she can laugh freely.
But from that day on, he is always listening for two things – growling of the walkers and Carol's laugh. One terrible and one beautiful.
As they are always on the move and running out of places to hide, the laughter is scarce now. That makes him do the strangest thing. He's teasing her and saying stupid things on purpose, just so she can tease him back. He's sure others will notice and he'd be a laughing stock, but nobody says a word. Maybe they're too busy with their own problems. The Grimes family is still coping with Shane's death. Hershel, Maggie and Beth are still mourning Otis, Jimmy, Patricia and the farm and they are getting used to the life on the road. Glenn is doing his best to help them. T-Dog... he isn't really sure what is T-Dog thinking, but he sure as hell doesn't care about what Daryl Dixon does. And everybody worries about the baby.
Daryl is grateful that nobody comments on him and Carol, because the whole things makes him so nervous that he feels like one wrong word would send him running away like a scared deer. Sometimes he thinks that Carol knows it too, because from time to time when he teases her she gives him this smile like she could read him like an open book. He doesn't like it and he would walk away if it were anyone else. But he can't walk away from Carol.
There is a brief moment, when he finds his brother, when he thinks it's over. He would leave with Merle because that's the right thing to do. Blood is thicker than water, after all, and it is certainly thicker than a woman's laugh. But Merle dies (a hero's death, ironically) and Daryl doesn't and all of the sudden he knows that Carol is the only person in the world that matters.
That's why, when Rick tells him what she did and what he did to punish her, Daryl doesn't say a word. He turns around, starts his bike and rides out of the gates. It takes him three weeks to find her, but he does, in the end. He discovers her lair in a mall, behind the counter of a baby store, and it doesn't take long before she returns there. She almost shoots him at first, of course, but after she recognizes him, she smiles like she knew he was not going to let her leave. Like she could read him like an open book, but this time he doesn't mind.
"You coming, woman?" he asks.
"Will you make me?" she winks, he rolls his eyes and she laughs.
They ride back together and he can see the looks people are giving her. A lot of them hate her, but she can take it. They used to hate Daryl too. Carol can survive some glaring. There's only one person that needs persuading.
When Rick comes out of cell block C, already angry, Daryl gets ready to make his stand. Carol is at his side, no longer cowering behind stronger people. Daryl looks Rick in the eye. He killed his own brother, he climbed out of a gorge with an arrow in his side, he fought walkers and people, he survived the "parental care" of his own father, and one Sheriff doesn't scare him. After all, Rick's authority is so weak, that it can be brought down by two words. Two simple words and for her laughter, he's willing to say them.
"She stays."