This cover was originally advertised as the cover for #6. Since it featured 'The Protectors', who guest-starred in the Rook's strip, one could assume that their origin story was to have debuted in #6, but was delayed for some reason until #11, while their guest-starring appearance here was used to prime the pump for their own series.
The previous Rook serial had set up some major changes in the Rook’s supporting cast and this issue’s story helped clear up some of the ramifications.
Although he’s never actually identified as such, Joe’s dad, DC’s Superman, guest-starred in Joe’s story.
This story is not based on any novel by Sir Arthur Conan Doyle.