Enid Blyton The Secret Seven set 3 book (Book 6,book 7,book 8)
 
Set included
Good work,Secret seven
Secret seven win through
Three cheers,Secret seven 
 
Good work,Secret seven
Peter and Janet are the only witnesses when a car is stolen. They saw the thieves, and now all the secret seven are involved. But when they realise they are on the trail of a dangerous gang, the Seven don’t feel quite so brave. This time, they might have taken on too much
Secret seven win through
The Secret Seven have a brand- new meeting place, but somebody else has been using it at night. With the help of a special addition to the gang, the Seven are determined to catch the cheeky intruder, whatever it takes…
Three cheers,Secret seven 
When peter and Jack go looking for  their lost model aeroplane  in an old abandoned house, they find a surprise, Who is living there, and why? Looks like the Secret Seven have another interesting case to solve…