Enid Blyton <br/><br/>
Good Old Secret Seven 

<br/><br/> There are strange happenings indeed at Torling Castle! Someone is hiding out in the ruined tower, making the resident jackdaws very unsettled. Who is it, and what do they want? The Secret Seven are on it... 
<br/><br/><label>ISBN: </label>9780340917657 
<br/><br/><label>Dewey Class. No.: </label>English BLY