Well Done, Secret Seven

This story's main characters are:

• Geoff
• Barbara
• Pam
• Peter
• Janet
• George
• Colin
• Jack
• Scamper
• Geoff's uncle
• Mr Tizer

The Secret Seven decide that they need a better meeting place for the summer. Colin comes up with the idea of a tree; this turns out to be a great idea because, firstly, it's a less stuffy meeting place during the hot summer days and, secondly, it's a great hiding place for Geoff. When Geoff eventually reveals why he is hiding, they realise they have themselves a mystery to solve.  Geoff tells them that one night he overheard his uncle and his uncle's friend (Mr Tizer) talking.  The only words he heard were MKX, Thursday the 25th, Emma Lane and a red pillow. 

The only part of that which made sense to them was Thursday the 25th because it was the coming Thursday.  But later in the story, they find out that MKX is the name of a mail van and that Emma Lane was actually a place called Emmer Lane and that the red pillow was a red pillar box!  With all these clues the Secret Seven deduce that Mr Tizer and Geoff's uncle are planning to rob a mail van carrying a valuable parcel inside.  Following the Secret Seven's detective work, the police are informed; when the robbery takes place the following Thursday Mr Tizer and Geoff's uncle are shocked to find the police in the back of the van instead of the valuable parcel!