Blood Brothers — Ruth Fox

Silvershine has changed since Zach and Monster-boy made their daring escape from the Grelgoroth. Now the Wall is gone and the citizens of North Silvershine are preparing to welcome the monsters into their city. But when a prominent leader, the mysterious Wolf-monster, Mr. Snow, takes an interest in Monster-boy, Zack is suspicious.

Zach's father's research into the ancient history of Silvershine has drawn the attention of Mr. Snow. And he isn't the only one with his evil eye on the old artifiacts; Ms. Cutter is snooping around, too.

And that's not all. Weird, inexplicable things are happening to the kids who escaped the Grelgoroth's lair. Lex is distant, and every kid at school is wearing odd silver badges.

As tensions heighten between monsters and humans, a dark plot grips the two brothers. Zach will find himself embroiled in a dangerous mission, one with far-reaching consequences for Silvershine Island, and for him and Monster-boy both.