Winter's Wraith

"-There is a potential in you that not many have, and I can make you much more. More than the loud, angry child that fights without his head.' He levels me with unnervingly calm eyes and nears me even more. 'Your revenge has come to an end, your family, friends, anything tying you to this life. I can change that. All you need to do is follow me and forget this... All of it.'"

They know them as assassins, guns for hire, mercenaries... That's all they know.
Pay them quickly. It never happened.
Riley had been consumed by a revenge so thick that he no longer knew the person he'd become.
His parents were murdered when he was a teenager, but he made those responsible pay very dearly.

A single letter. That's all they know about her.
K.

She has absolutely no concern whether she lives or dies which is exactly why she got their attention. Riley may just collide with someone who is equally as detached from the world as him.
But no where near as crazy...