The weight of silence / Heather Gudenkauf.

When two seven-year-old girls go missing, all are under suspicion. Calli Clark is a dreamer. A sweet, gentle girl, Callie suffers from selective mutism, brought on by a tragedy she experienced as a toddler. Her mother Antonia tries her best to help, but is confined by marriage to a violent husband. Petra Gregory is Calli's best friend, her soul mate and her voice. But neither Petra nor Calli have been heard from since their disappearance was discovered. Now Calli and Petra's families are bound by the question of what has happened to their children. As support turns to suspicion, it seems the answers lie trapped in the silence of unspoken secrets.