The book arrived on our nineteenth birthday with no return address, just our names written in silver ink that seemed to shimmer against the black cover: *Maya & Sage: A Story of Vengeance*. We laughed at first. What kind of weird birthday prank was this? Then we opened it. Chapter One described our childhood with unsettling accuracy—the treehouse Dad built in our backyard, the matching scars on our knees from when we crashed our bikes in tandem, even the secret language we'd invented when we were six. Details no one outside our family could possibly know. Chapter Two detailed our present. Our college classes. Our apartment. The coffee shop where Maya worked, and the library where I spent most of my time. Chapter Three made us stop laughing. *Maya's body was discovered in the warehouse district on a Tuesday. She'd been missing for three days. The detective said she'd suffered, but Sage couldn't hear the details through the roaring in her ears. Her twin, her other half, was gone. And someone would pay.* I remember Maya's face going white as we read ahead, our hands trembling as we turned pages that detailed my descent into obsession, my transformation into someone I didn't recognize. A vigilante. A killer, eventually. All in the name of avenging her. The book had fifteen chapters total. By