Coyote's Kiss (Supernatural #8)

A truck full of illegal Mexican immigrants slaughtered with supernatural force is found by the side of a road. Trying to find answers, Sam and Dean are plunged into the dangerous world that exists along the Mexican border. 

They encounter a tattooed, pistol-packing bandita on a motorcycle who seems be everywhere they go before they get there. Xochi Cazadora draws them into a whole new world of monsters...

A Supernatural novel that reveals a previously unseen adventure for the Winchester brothers, from the hit TV series!