According to the legend, there once was a beautiful queen who loved music. She was beloved by all the people of Ambrosia. But one day, the queen became very ill. The people were desperate and tried to make a medicine that would heal her. Unfortunately, it was not completed in time, and the queen passed away. The medicine turns out the be the Elixir for Eternal Life. All the people of the city drank the Elixir, in the hope that they could be with their queen once again (in the opera performed by Janice Quatlane this actually happens at the end).
Later, while playing the game for eternal life, it turns out that the legend is true, and that Ambrosia lies buried under an island. After Professor Layton, Luke, and the other remaining candidates make their way to Jean Descole's castle, it is revealed that Descole had an even bigger plan in mind: to revive Ambrosia.
According to the legend, this can only be done when all the songs of Ambrosia are played together. Descole kidnaps Melina and forces her to sing the Song Of The Sea, while he plays the Song Of The Stars on the Detragan. When nothing happens, Descole becomes furious and transforms the Detragan (together with his castle) into a giant robot, in order to use it to bring Ambrosia back up by force.
He is later stopped by Layton, who tells him that he missed another song: the Song Of The Sun. Layton asks Janice/Melina to sing the Song Of The Sea again, while he himself plays both the Song Of The Stars and the Song Of The Sun on the Detragan, causing Ambrosia to finally show itself.
In the end, it was believed that Melina might have been the long-awaited reincarnation of the queen of Ambrosia.