Monica Stephens never knew her birth mother. Raised by a strict but loving adoptive parent, she blossomed into a woman with a thriving career as a pediatrician and a family of her own. But sometimes, she wondered about her origins. Especially her biological mother.

Until Grace arrives.

Confessing to be the birth mother Monica had long wanted to meet, Grace quickly becomes an indispensable member of the Stephens household. Cooking their meals. Looking after the children. Comforting Monica when the family dog is inexplicably killed. Tending to Monica as she falls ill to a mysterious sickness that, every day, makes Monica look and feel older.

Meanwhile, Grace is looking better. More vibrant. More youthful. More seductive . . .

Monica's husband, Troy, knows something is up. He launches an investigation into the woman who demands to be called "Nana," and has taken over his home.

But the truth is beyond their wildest imaginings.

It seems Grace has done this before . . .