The Kane house in late autumn always smelled like pine from the early Christmas tree and the faint, comforting scent of hot chocolate that seemed to linger year-round. One quiet Sunday evening, with snow falling soft and steady outside the windows, the three Kane siblings found themselves alone in the living room while Rowan and Holly finished dishes in the kitchen.

Lily (twenty-four, fresh off her first pro season in Boston, home for a rare long weekend) sprawled on the couch in ...