IT’S HARD for me to remember exactly what I was told about the details of Alison’s death when it happened, and what facts I acquired later on. I’m fairly certain I didn’t know it was the actor who’d found my sister, or who he was to begin with. But at some point I must have learned this, because there were two periods during my adolescence when I became oddly fixated on the actor. The first such period was in fifth grade. I often had sleepovers on the weekends then, which typically involved renting a movie. If the sleepover was happening at my house and it was my parents taking us to Blockbuster, I would do everything as usual, and we would come home with Free Willy or Homeward Bound or something like that. But if I was sleeping out and it was someone else’s parents taking us, I’d try to make it happen that we would rent one of the actor’s movies. The actor was not in children’s movies, so this involved convincing my friends that a film about a bank heist or prohibition-era Chicago was something we would like. “This is supposed to be hilarious,” I’d say, or, “I heard this is Sean Sawyer’s favorite movie,” Sean Sawyer being the boy we were all in love with. “Are you sure?” the mom or dad would ask when we handed them our selection, and if I’d done a good job, my friend would nod just as enthusiastically as me. Because the movies were actually not at all the kind of thing that interested us, often my friends would doze off after not too long, and then it would just be me, on a beanbag cushion in their playroom in the dark, watching the actor and looking for something I couldn’t explain.

The second period came a few years later, when I was thirteen or fourteen and my friends and I were obsessed with YM and Bop and at night I dreamed steamy soft-core dreams about the shy, sensitive members of various boy bands. For a while during this time, I played out these extended scenarios in my mind where the actor reached out to my family seeking resolution, which he found in talking with me. Our unlikely friendship led to invitations to be his guest at awards shows, where I wore gowns and was photographed on the red carpet, stoic beauty radiating from me like an aura, and I won the attention and sympathy of all the stars I adored. I was ashamed of these fantasies, but I was helpless to stop them, unable to resist the maudlin potential of my own story. I thought I was awful, but now I think I was no more awful than any teenage girl—I simply had more potent material to spin.

I LOST my virginity in tenth grade. My boyfriend was a bassist in a band called Skar Tissue and a budding cartoonist who drew pictures of me with big anime eyes and hair made of flowers. His own hair was black streaked with violet. I helped him dye it every other week in his bathroom. My hands were perpetually stained purple, as if I’d gorged myself on berries. For as long as we were together, I was a skater girl, which didn’t mean I skated, but rather that I stood around with a few other girls while the boys skated. I wore thick black eyeliner and dog cuffs on my wrists and slouched proprietarily against the gym wall when Skar Tissue played at school dances. At homecoming, they debuted a song called “Emily.” I was a girl whose boyfriend wrote songs for her and played them in front of the whole school. I marveled at this, held it proudly in hand.

Four months after we started dating, on a night when my parents were at a dinner party in Toluca Lake, I told him I was ready. He treated me like I was made of glass, and I liked this. He treated sex with the seriousness of death, and I liked that, too. Afterward, it occurred to me that if Alison were alive, I would have told her every detail. Then something else occurred to me: If Alison were alive, it would not have happened at all. There was another life I might have been living, a life in which I was not Emily of Pasadena, but Claire. This other life ran alongside mine like the scenery falling away at the side of a speeding train. While Emily had sex in Southern California, Claire wrote up the mealworm lab in New York. Emily was pink-skinned from the California sun, her white-blond hair cut in a stylish crop. Claire was pale as flour, her haircut the same since she was five. What was I supposed to do with the fact that I was thrilled, I was so very relieved, to be Emily and not Claire?

I KNEW the exact day I outlived Alison. Eighteen years, three months, twelve days. I had calculated the date when I was fifteen, working it out in the back of my notebook as Magistra Kouchner chirped Latin conjugations. Io credo, tu credi, lui crede. For years, I dreaded the day. When it finally arrived, I marked it in secret. I considered telling my friends, who were at that time packing up one by one and saying tearful farewells as we scattered to the well-regarded colleges we would attend. (I would be the last to leave, bound for a highly ranked liberal arts college in the Midwest.) In the end I told no one. I was suspicious of my own impulse to calculate and mark the date. It seemed a theatrical and self-absorbed thing to do. Maybe part of what it means to be eighteen is to feel perpetually caught between the intensity of one’s desires and the dawning self that judges them.

On the morning of the day I outlived Alison, I awoke to find my world suffused by a peculiar falsity. The sunlight streaming through my bedroom window seemed incorrect somehow, a shade too lemony. When I walked into the kitchen, where my mother was eating a bowl of cereal, and she said good morning, her voice, too, seemed to have shifted, like a piano gone almost imperceptibly out of tune. All day I couldn’t shake the feeling that I had been transferred in my sleep to a vast simulacrum. I drifted from room to room, picking up and setting down books, beginning and abandoning the tidying of my bedroom, sitting in the garden, and then, shaken by a sense that I’d remained there too long, moving to the living room. Even my own face seemed to me a not-quite-right facsimile—I studied myself in the mirror and saw Alison’s features skewed just enough to look distorted and unharmonious, my pale skin and hair like some ghostly afterimage. I’d been awaiting this day for years, but I don’t think I ever really expected it to arrive. Now that the critical juncture was behind me. the tension went out of everything. My world hung slack as a sail on a windless day.

WHEN I arrived at college, for the first time since I moved to Pasadena as a girl, I found myself regularly around people who didn’t know me or my story. The usual challenges and possibilities of freshman year—making new friends, conveying one’s identity to others (with some fresh tweaks and adjustments from one’s high school iteration)—were complicated for me by the knowledge that at some point I would have to tell these people who I was, which is to say, who my sister was. I can’t express how much I disliked doing this. Though I’d come out of my shell in Pasadena, I was still relatively shy, and there was simply no way to tell people that I was Alison Thomas’s little sister without drawing attention to myself.

The worst part was seeing people’s surprised reactions. I don’t mean the inevitable surprise of realizing that someone you know is connected to such an infamous incident. I mean the surprise, plainly visible on their faces, that this had happened to me, that this story was my story. How confused they seemed, how disappointed: something had happened to me, something huge, and yet, somehow, I had managed not to be made interesting by it.

I DATED a few boys in college. There was Nick, a pre-med soccer player who loved nothing so much as the sight of me topless in his uniform shorts. Avi was a stoner from Toronto. Scattered between these longer relationships were brief interludes with Dave and Jordan and Zeb (whose first name was really Richard), all of them so different from one another it was like trying on funny hats in a store. With each of them I changed, shape-shifting until I fit into their world. I prided myself on my chameleonic transformations, and on not having a “type,” which I thought indicated that I was open to the world, and that my essential self was so solid it could inhabit any number of forms.

They had different approaches to getting me to talk about her. But one way or another, they all tried.

“I just want you to know you can be completely open with me. Like, if there’s ever anything you want to talk about.”

“My uncle died when I was seven. He was basically my second dad. It really fucked up my world, you know?”

“You don’t have to talk about it if you don’t want to.”

I could never shake the humiliating sense that, whether they realized it or not, these boys were in love with some idea of me as a tragic, wounded girl, that when they looked at me they saw a sort of double exposure—me and the sister I had lost, a second self whose presence they could sense whenever they were with me, and that it was she, not me, they were really after, that as they kissed and licked and squeezed me they were trying to draw themselves closer to her, to touch the infinite, exquisite void of a beautiful, lost girl.