The Black Rose mystery is one of the longest and most complex modular storylines in 80 Days. It may happen after every two complete journeys around the world, starting after the first one. It begins on the London-Paris train, where Passepartout may encounter a man who has lost a silver cigarette case. A black rose is all that is left for the man. Later on the journey it is discovered that the silver cigarette case has been stolen by the infamous Black Rose, an international thief of jewels and other valuables.
The rest of the Black Rose storyline is split into different stages. They do not all have to be completed in one specific order, and some need not be completed at all.
Stage 1: On the Blue-Line ferry running from Nice to Tunis, Passepartout will meet a young and compassionate lady named Estelle. She longs for adventure, and if Passepartout pursues the correct paths she may request to travel with Fogg and Passepartout for the remains of his journey. When the Blue-Line arrives in Tunis, Estelle will travel with Passepartout and Fogg aboard one of the Ottoman airships traveling to either Luxor or Beirut. She will leave soon afterwards, already tired of adventure.
Stage 2: Passepartout, regardless of whether he travelled with Estelle, will discover the lost cigarette case from the Amphitrite Express. It will come with a note (more personalized if Passepartout travelled with Estelle), and will be valuable in one Indian city. This stage will always occur.
Stage 3: On various routes, Passepartout may find someone leaving his compartment in a train or airship. No matter what he attempts, he will not be able to catch the thief.
Stage 4: Passepartout may awaken several times on any route or city in the game to discover that either an item has been stolen, money has been placed in his suitcase, or a black rose has been placed on his bed. These will usually come with a mysterious note.
Stage 5: On a journey passing through India (usually to the city where the cigarette case is valuable), or in an Indian city itself, Passepartout might awaken to find that Estelle/The Black Rose is inside of his room. The Black Rose will explain her plan; To steal the stockpiled wealth of the worldwide Artificer's Guild. She believes that this wealth is kept on a floating airship somewhere in the Atlantic, but she has not discovered its exact location. As long as Passepartout continually makes positive and agreeable remarks, The Black Rose will tell Passepartout that they will meet again. Passepartout may continue to receive notes and items from the Black Rose after this.
Stage 6: From here, it is necessary that Passepartout travels to Buenos Aires from either Santiago, Asuncion, or if Passepartout reads a newspaper about the Black Rose being captured (this is a ruse to throw off the Artificers), Rio de Janeiro. In Buenos Aires, Passepartout must gain access to the 'upper city', simply by traveling to it and declaring that he is 'Passepartout, valet of Phileas Fogg'. Fogg and Passepartout be granted access to the upper city, but while in the elevator leading upwards they shall be accompanied by the Black Rose, disguised as Lady Aodha.
It turns out that Buenos Aires is the home of the Artificers' Guild. As long as Passepartout does not report Aodha/The Black Rose, she will accompany them through the various parts of the upper city. The head of the Artificers' Guild will grant them permission to travel aboard the airship El Dorado, which travels to Dakar.
Stage 7: From here, the group must board the El Dorado. During the journey, the Black Rose (whose true name is Stelle, similar to Estelle from the Blue-Line) may reveal to Fogg and Passepartout that she is the bastard daughter of Fogg and a maid who worked at the Reform Club in London. Passepartout is duly shocked by this, but Fogg says that it is true.
The search for the hidden wealth of the Artificers' Guild aboard the island continues. It is entirely manned by automatons, which the Black Rose assumes is because they are not tempted by wealth, who run and maintain the island. Passepartout will eventually discover an injured, stuck automaton. If he convinces him to talk, Passepartout will discover a hidden door that leads to a huge cavern underground. With the Black Rose, he will travel there. The rest of the story on the El Dorado is best to be discovered by the player.
Stage 8: Leaving the vault and getting off of the El Dorado, Passepartout will arrive in Dakar. He may enter a romance with the Black Rose/Stelle/Estelle/Aodha, and is given the choice between sticking with his master or going away on an adventure with Stelle. If Passepartout agrees to go with Stelle, three routes appear from Dakar: To New Orleans, Budapest, or Cairo. Taking any of these routes will cause Passepartout to depart from his master and live a life of adventure and love. The game will end.
If, instead, Passepartout goes with Fogg, the journey will continue as per normal until they arrive in London. Upon arriving either triumphant or disheartened in London (depending if they arrived in under 80 days), Passepartout will notice in the crowds a single woman in disguise. She is the Black Rose, and she gives Passepartout one last wink before disappearing into the crowd. Passepartout may choose between going home with his master or go into the crowd to join with Black Rose. Regardless of the choice, the game will end here normally, with the newspaper display and the restart of the game.