What I Believe — Norma Fox Mazer

When Vicki's father is laid off from his job, everything changes. Her family moves to a city apartment, and Vicki has to forge a new path at her urban school. Worst of all, one night her depressed father simply disappears. Vicki soon finds herself living a double life--fine on the outside, anything but fine on the inside--and that leads to a moral dilemma she's ultimately forced to confront.