How do you solve the Black Rose mystery?

One of the longest and most complex storylines in the game is the Black Rose mystery. This storyline will only happen after every two complete journeys around the world, starting on the second one.

What starts the Black Rose mystery is when you meet the man who has had his silver cigarette case stolen on the Amphitrite Express, the submarine-train joining London to Paris across the English channel. If you are unable to get the Amphitrite Express from London to Paris you can go through the Blue-Line ferry running from Nice to Tunis where there will be a young mademoiselle named Estelle that Passepartout can carouse with that will start the Black Rose mystery. The story then continues through random events while sleeping in hotels around the world.

You will find El Dorado, the hidden floating city under the control of the Artificers' Guild off the coast of South America near Buenos Aires. Once there you must do the following:

Step 1 - Walk up the hill

Step 2 - Discover the Artificer with broken legs

Step 3 - Investigate patch of grass

Step 4 - Find vault

Step 5 - Go with Black Rose