Journalist Emma Clark travels to Switzerland in order to continue her investigation into her boyfriend's old flatmate Clara Torres, an art student who mysteriously vanished after becoming obsessed with an avant-garde painter, Ursula Blum.
Shortly after arriving in Switzerland, Emma visits a small exhibition dedicated to Ursula Blum at a cultural center in Geneva. The building where the center is located used to be the sanatorium where Ursula spent her last years of life.
Emma visits two of the paintings that Ursula painted in the sanatorium with Christina, an employee of one of the museums. With Christina's help, Emma begins to understand what Ursula seemed to be trying to represent with her paintings.
After discovering some information about Clara's life with the help of one of her friends, Emma travels to Lugano to see the last painting Ursula painted. There she hears a local legend attributed to the painter.
Emma travels to St. Gallen to visit its abbey, where she hopes to obtain information about the neumes that appear in Ursula Blum's scores. Upon leaving the abbey, Emma approaches the cemetery where Ursula is buried.
Emma returns to Basel to interview the restorer of a Blum Box, one of the music boxes manufactured by Victor Blum, Ursula's cousin. Later, she meets with Christina, and together they develop a hypothesis.
Emma manages to decipher a hidden melody in Ursula Blum's paintings with the help of Sonia, the friend at whose house she is staying. The next day she visits the Museum für Gestaltung in Zurich to try the melody out on a Blum Box.
Emma meets Oliver Davis in Bern, a collector who claims to have a Blum Box. From his description, Emma suspects that it could be the box with which Ursula and Victor posed in the photo at the Photo Elysée museum in Plateforme 10.
