Series numeration from GoodReads.

For many long years, Atlee Pine was tormented by uncertainty after her twin sister, Mercy, was abducted at the age of six and never seen again. Now, just as Atlee is pressured to end her investigation into Mercy's disappearance, she finally gets her most promising breakthrough yet: the identity of her sister's kidnapper, Ito Vincenzo. With time running out, Atlee and her assistant Carol Blum race to Vincenzo's last known location in Trenton, New Jersey -- and unknowingly stumble straight into John Puller's case, blowing his arrest during a drug ring investigation involving a military installation. Stunningly, Pine and Puller's joint investigation uncovers a connection between Vincenzo's family and a breathtaking scheme that strikes at the very heart of global democracy. Peeling back the layers of deceit, lies, and cover-ups, Atlee finally discovers the truth about what happened to Mercy. And that truth will shock Pine to her very core. -- from book jacket.