The Silent Ones book by William Brodrick

Find out why Harry is prepared to blame an innocent man. That's the thread. Follow it. You'll reach the Silent Ones.
Eleven-year-old Harry Brandwell, obviously in great distress, refuses to talk. What, or who, is holding him back?
When a homeless man arrives unexpectedly at Larkwood Priory, the community welcomes him with open arms. But he isn't what he seems: he knows why Harry won't speak.
Father Anselm finds himself on the trail of an impostor, unaware that he is being drawn into the shadows of a mysterious conspiracy, his reputation for integrity exploited by those closest to him. With his attempts to pursue justice thwarted at every turn, it is clear that there are those who eagerly await his downfall. As he is lured into the courtroom to defend a man he believes to be innocent, Anselm begins to doubt his own judgment.
Meanwhile Harry Brandwell, abandoned and betrayed, has decided to take matters into his own hands. But Anselm is completely unsuspecting. He's in the dark, seeking the Silent Ones . . .