The frost still clung to the windows, even though the calendar read May. It wasn’t the weather, not truly—it was the lingering chill that Emma Carter sometimes swore followed her from the other side. Some mornings she woke feeling as though a ghost had brushed its hand across her cheek. Other times, it was the feeling that someone—or something—was waiting. Watching.

Emma stared at the faint steam rising from her teacup. She sat cross-legged on the edge of their flat’s small balcony, ...