It is when a mission goes wrong that he realizes what he should have realized months before.
She leaves the van the moment it is parked, a few blocks away from the building she is supposed to steal documents from, the deep red wig shines through the night as she walks towards the building and he watches her retreating back.
He hears a little pop when she switches the comm link on and quietly listens to her as she walks. When he can barely hear her breathing, he knows she has reached the building and is on her way in. Her voice - 'going in' - confirms it to him and he is slightly (but not really) surprised at how well he knows her.
"One guard," she says, and he is relieved, because she can take out one guard easily. It takes two seconds and he hears her strike - someone falling to the ground and a triumphed half laugh. "Down."
There are ten minutes of silence as she finds her way through the building and he hears noises of what he assumes is Sydney taking care of a lock. "In Ezcurra's office," she reports once the noises stop.
"The safe should be somewhere on your left."
He waits until she finds it, and then they wait together as Marshall's latest invention figures out the combination.
"You shouldn't have gone alone."
Her reply is harsh. "I can handle a safe and a bunch of papers."
Then there is silence. He tries to listen but it's hard to know what she's doing - though he guesses: opening the safe, looking over what's in there, taking what they need, leaving.
It takes too long and he hears nothing. He wonders if she went radio silent because she's pissed, but decides against it.
Suddenly he hears her again. "Vaughn, they saw me," and everything happens so fast. He hears her running, and fighting. In horror he realizes she was knocked down to the floor, and that there are at least five people around her. She kicks - tries to, at least - and he knows she got hurt again when a painful breath is sucked in sharply.
"Where are you?" he calls and jumps out of the van. "Third floor!" she calls back and as he runs he listens to her getting more hurt. He starts to run faster.
A foreign voice speaks in his ear. "No need to come, we're taking her with us," and he tries to run even faster, and his earpiece makes a static noise, and he knows he won't hear anything else from her.
He takes his gun out when he reaches the building, holds his arm out, and waits. One minute passes and six guys come out, two of them carrying what seems to be an unconscious Sydney. He shoots, once, twice, and one guy falls. They drop Sydney to the floor and shoot back, and he runs towards them, shooting and screaming at the same time.
He starts fighting one of them, two of them, and shoots a third one, who cries out loud and drops down. Why isn't she waking up?
Two of the guys try to grab him but he avoids it, and shakes her shoulder. "Sydney!"
A guy laughs, and gets his nose broken in return. He shoots a few more times, careful not to hurt Sydney, and two more guys fall. There's only one left, and when he speaks, Vaughn knows it is the one who talked to him through Sydney's earpiece.
"You came anyway." It's a statement, and Vaughn doesn't waste a moment before kicking and spinning and smacking and hitting the guy in the head with his gun.
Quickly, he picks Sydney up and carries her back to the van, where he places an icepack on her forehead and impatiently waits for her to wake up.
When she finally does, she gives him a confused look and he hugs her tightly as she looks around. "You took out all those guys yourself?" she asks, and he doesn't answer, just inhales her scent and entire being.
He doesn't realize he is shaking until she places a hand on each of his cheeks and looks into his eyes. "Are you hurt?"
He shakes his head and tightens his hold on her. "I thought I was gonna lose you again."
She understands and speaks softly. "You didn't."
He buries his chin in the fake red hair. "I love you, Syd."