Mattie trotted insistently after Nick, clearly not willing to take no for an answer. In fact, she shoved him to the ground––on his stomach––and straddled his back, brandishing the knife in white knuckles. "You never fucking listen to me even when you're fucked up on magic-ass demon drugs," she hissed. "I am cutting that shit out." 

And that was how she ended up making shallow, quick slices at an angle into Nick's back, surrounding the black stripes.