The Weight of Silence by Heather Gudenkauf

One August morning, two families in Iowa awaken to find their little girls, Calli Clark and Petra Gregory, missing. Calli, a sweet seven-year-old who suffers from selective mutism, hasn't spoken since a childhood tragedy. Her mother, Antonia, fears her decision to stay in a troubled marriage may have cost her more than just Calli's voice. Petra, Calli’s best friend and voice, has also disappeared.

As the search intensifies, the Gregory and Clark families are bound by the mystery of what happened to their daughters. The truth, hidden in silence, lies within the unspoken family secrets they each harbor.