Silent to the Bone by E.L. Konigsburg

When he is wrongly accused of gravely injuring his baby half-sister, thirteen-year-old Branwell loses his power of speech and only his friend Connor is able to reach him and uncover the truth about what really happened.

Liz says:

“This is an exciting, well-written mystery filled with complex relationships. While many 6th graders do read this, i usually recommend it for 7th graders.”