My son slides under the daybed, flattening his sprawling limbs in all directions across the dusty floor, then retracting them with a jerk. “I’m making myself invisible!” he declares. He knows our news is unwelcome. Don’t let him think it’s because of him, his doctor had coached. Crouching, I reach my hand to stroke his arm — a gesture I realize is not enough to comfort a boy whose body short circuits with uncertainty. My husband and I tell him: You can’t start second grade tomorrow. We’re leaving Singapore. We’re moving to America. We don’t know when. It will be...