R. Austin Freeman 
The Eye of Osiris 

John Bellingham is a world-renowned archaeologist who goes missing mysteriously after returning from a voyage to Egypt where fabulous treasures have been uncovered. Bellingham seems to have disappeared leaving clues, which lead all those hunting down blind alleys. But when the piercing perception of the brilliant Dr Thorndyke is brought to bear on the mystery, the search begins for a man tattooed with the Eye of Osiris in this strange, tantalisingly enigmatic tale.