The Tragedy of the Korosko (1898) is a novel by Sir Arthur Conan Doyle.
It was serialized a year earlier in The Strand magazine between May and December 1897, and was later turned into a 1909 play Fires of Fate.
They are sailing up the River Nile in "a turtle-bottomed, round-bowed stern-wheeler", the Korosko.
They intend to travel to Abousir at the southern frontier of Egypt, after which the Dervish country starts.
It also reveals the very great suspicion of Islam felt by many Europeans at the time.