There’s a tantalizing premise in the new novel “Familia” by author Lauren E. Rico. As a fact checker for a popular magazine, Gabby DiMarco deals in that increasingly vague commodity — “truth.” And when she takes a DNA test, she discovers something her deceased parents would have sworn was impossible: Gabby has a sister.

But does Gabby WANT a sister — even one who desperately wants to meet her? And if it’s true, why were they separated to begin with?

Rico discusses and signs copies of “Familia” Tuesday at Bank Square Books in Mystic, and writer Jeannie Moon (“Then Came You”) moderates.

Lauren E. Rico, 5:30 Tuesday, Bank Square Books, 53 W. Main St., Mystic; free, books available for purchase; banksquarebooks.com, (860) 536-3795.