I knew how Emma felt. Every single time I watched my adopted father put an arm around her shoulders, I was sure that would be the time he realized that she was an impostor. That he’d finally see that I was gone. It wasn’t jealousy, exactly—I didn’t begrudge Emma that love—but the world had moved forward, and no one had noticed that the girl living my life wasn’t even me.

Emma played with the zipper pull on her jacket, her voice suddenly small. “Dad, did you suspect? Before Becky told you, I mean? Did you ever think there might have been two of us?”

Mr. Mercer turned to look at her, his lips twisted in thought. “No. But then again, you yourself were such a surprise it was hard to know what to think. Becky was only eighteen when she came home with you. We hadn’t seen her for more than six months. We hadn’t even known she was pregnant, and then all of a sudden she rang the doorbell with you in her arms. It was just before Thanksgiving, and you were only a few months old.” A fond smile curved across his face. “You were such a sweet baby. And tiny, impossibly tiny. Becky told us you’d been several weeks premature—of course, now we know that your size was because you were a twin.” His voice caught for a moment, then he recovered. “We loved you from the moment we saw you. We would have loved both of you, if only we’d known.”

Emma nodded. “Mom’s taking this really hard, isn’t she? The news about Emma?”

They were passing under a streetlight, and in its lurid yellow light she could see the deep shadows in Mr. Mercer’s face. “Of course she is. We both feel terrible. Sutton, Emma was just like you at the beginning. Thinking about how difficult things were for her is hard, because it’s so easy to imagine you in her place. It could just as easily have been you that Becky kept secret from us. And now . . . well, it’s too late to do anything for Emma. And that breaks your mother’s heart, and mine.”

As they turned a corner, headlights lit up behind them. Emma glanced around to see a midsized Audi, creeping slowly in their wake. She drew in her breath, instantly on edge. “Let’s go this way,” she said, lacing her arm through Mr. Mercer’s and tugging him down a side street. Drake’s tags jingled as he trotted along ahead of them. She wanted to see if the Audi would follow them. Sure enough, the headlights turned, too.