Enid Blyton <br/><br/>
Three Cheers, Secret Seven 

<br/><br/> Who is hiding in the abandoned house? When Peter and Jack search for their lost model airplane, they realize the house isn't empty after all... 
<br/><br/><label>ISBN: </label>9780340917619 
<br/><br/><label>Dewey Class. No.: </label>English BLY