This episode of Superintendent Slade’s Case-book is titled “The Secret Sign” and appeared in Boy’s Own Paper 1956 (August issue) pages 44, 46 and 58. As usual Tom Kerr illustrated, why some of these are comic strips and some text, I don’t know
The solution below – don’t cheat!
SCROLL DOWN FOR THE SOLUTION….BUT DON’T CHEAT, SUPERINTENDENT SLADE IS WATCHING YOU!
SOLUTION