This is old and no one might be reading it anymore, but... what's the similarity between the three characters?
Wish i knew what the similarities were between the 3 characters.
WE'VE BEEN BAITED
OUTSMARTED
TLDR: There is someone faked their own death on those books.
It becomes hint to class Q that the class A murder victim is not actually dead and it's faked.
-Sherlock Holmes from the story 'The Final Problem':
It was intended to be the final Holmes story, ending with the character's death, but Conan Doyle was later persuaded to revive Holmes for additional stories and novels.
The truth is Holmes didn't fall into the waterfall
https://en.wikipedia.org/wiki/The_Final_Problem
-Lawrence Wargraves from Agatha Christie's 'And Then There Were None':
Wargrave persuaded Armstrong to help him fake Wargrave's own death
https://villains.fandom.com/wiki/Lawrence_Wargrave#The_Ten_Soldier_Boys
-Ellery Queen's 'Egyptian Cross Mystery': I think it's not Ellery himself, but rather character in that book named Andrew Van.
Andrew Van, is not actually dead.
http://www.dondammassa.com/Zquee.htm
But one fact stood out: Andrew Van had killed somebody and left the corpse of that somebody in his hut dressed in the rags of Old Pete; which is to say, dressed as himself. Then here was deception!
http://detective.gumer.info/anto/queen_16_2.pdf
page 225