W.E. Johns 
Sinister Service [EPUB ebook] 

Lance Lovell is a British counter-espionage officer. His younger brother, Rodney, unaware of this, asks Lance to let him come with him on one of the trips he is so frequently making, and after some demur Lance agrees. When Rodney has shown his quality he becomes a sort of unofficial assistant to Lance, and the two fare forth together on dangerous errands. On the successful conclusion of their exploits, Rodney expresses the opinion that, in comparison with the Secret Service, any other occupation would seem tame.