After spending many months in Britain training to be spies, Henderson’s group is ready to start a multi-month mission in  France. Their mission is to find ways of disrupting the German U-Boat (submarine) programme, that are slowly pushing Britain back from their command of the oceans. It’s dangerous but needed, particularly now as the German forces are fighting heavily against the british. The sabotage has to be on low level, otherwise there will be consequences. But just how discreet can the six kids make it?
A classic Muchamore novel, Grey Wolves returns back to  France after Secret Army, the previous novel, which was largely based in Britain. With reading Grey Wolves, I’m glad that we get to see more of France in one long,  mission, full of suspense.