Claire’s hand went cold in mine. “That is impossible,” she whispered. “Our parents only met when they moved onto the same street.” Dr. Lawson turned one monitor toward us. “Both of you carry the same rare gene variant, and the odds of that between unrelated people are tiny. Before I say more, I need a truthful answer. Did either of your parents ever hint at a connection?” I shook my head.

Then both our phones lit up at the same instant. My mother’s name glowed on mine, and Claire’s mother’s name on hers. A text from each arrived seconds later, word for word the same: “Please do not take any more tests. We are in the parking lot and we need to tell you something first.” Through the office window, I saw two women hurrying toward the entrance, holding hands, and one of them was crying.