Puzzle for the Secret Seven

The Secret Seven are Peter and his sister Janet, Jack, Colin, George, Pam and Barbara. They meet every holiday in the shed at the bottom of Peter and Janet’s garden – and solve mysteries, and eat lots of delicious food. But no one can enter the shed without whispering the secret password! There are 15 Secret Seven novels, and a collection of short stories. The gang witness the horror of a house going up in flames! Then there’s the theft of a very valuable violin. Are the two events connected? The Seven need to use all their detective know-how to find out