Hold Me in the Dark by Helena Newbury

I’ve been an FBI agent for ten years and I’ve never seen anything like this. A serial killer whose victims have nothing in common, who covers the crime scenes in equations even our best people can’t solve. Only one person can help: a mathematical genius who shuns society.When I track her down, she’s nothing like I expect: a fragile beauty who takes my breath away, her body broken and her soul scarred. She’s locked herself away from the world and somehow, I have to drag her into the light.
But as we work together, something starts to happen.
I don’t have friends. But she starts to feel like a friend.
I don’t have a partner. But she starts to feel like a partner.
I don’t fall in love. Not after what happened. But….
I look into her eyes…and I can’t look away. I glance down at her lips and I find myself leaning forward. There’s a soul-deep longing neither of us can fight. We might be the only people who can fix each other. But I have to resist. If she knew the secret I’m hiding….
When the case turns dangerous, all I want to do is protect her. But she’s as stubborn as I am. She’s the bravest person I’ve ever met. And she leaves me no choice.
This case could destroy us both but the only way we’re solving it…is together.