Enid Blyton 
Good Work Secret Seven! 
Secret Seven #6

Bonfire Night is quite near and the Secret Seven are looking forward to it. But an adventure looms when Peter and Janet are in the back of their father’s car, which is suddenly stolen. Following the clues they have, the mystery takes them to Sid’s Cafe where Peter has the brilliant idea of watching the cafe disguised as a 'guy’, with a mask, a red scarf around his neck and a wig made of black wool! Will he be able to listen and watch without anyone noticing?