Vulpes is not a soft man. He has never been broken, and he has never begged for anything in his life.
He wants to beg her to stay, and so he does. He tells her that he can save her from Caesar's wrath by making her his wife. She will be protected, she will never want for anything, and she will be his without boundary.
Underneath the Legion flag, she will also be his slave.
It is an old argument, one they have had before, and it works as well as the last time they had it. She shakes her head, and her soft refusal breaks him.
"I won't be your property," she says, shaking her head. "I will not allow the Legion to stand. I can't." The apologetic tone her voice takes is too much for him to bear. He hugs her tightly, and entertains the notion of taking her with him anyway, despite her protests. He finds he can't stand the thought of the love in her eyes transforming into a burning hate for the rest of their lives.
"Is desertion your choice?" he asks hoarsely. She nods.
"It is."
"I'll have to follow you," he says.
"I know."
"I'll have to kill you the next time we meet," his voice trembles, and she meets his gaze.
"I know."
She leaves him, and nothing he can say can change her mind. He gives her a day's head start before forlornly gathering his weapons to hunt her down.
He tracks her through the Mojave to a place called The Canyon Wreckage, where dead husks of the old world lean on each other to keep from collapsing. The words "Courier Six" and "You can go home now, Courier" send a chill up his spine. They call out across a vast expanse of time like a lover's voice to tempt her away.
The Divide is beyond the wreckage. He isn't sure what would be worse; a death by the Divide, or a death by his hands. So he bides his time and waits for her. Caesar is pleased when he hears of her new location. He feels she'll die for sure, and Vulpes both fears and hopes he is right.