Somwwhere in the middle of the north sea,invisible to the ordinary human eye,which would only see churning black waves and perhapes an odd concentration of shrouding mist,was a small island.The summer night air surrounding it was deathly cold,and despite the gusts of winds that blew from all directions against it,strangely silent. Except for one sound: a low,rasping chourus of breathing,issuing from tallhoodedsilohouettes that like an impentable black circle,ringed the massive grey stone walls ofwhich rose looming upon the island:the Fortress of Azcaban.