Stage Fright

from the synopsis:
Stage Fright centres around the Royal College of Music in Middenheim. The player characters are at the opera, seeing the matinee of The Marriage of Fibonacci on its penultimate day of performance.
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Antonia Rivera-Salazar Flores, an Estalian singer of some renown ... is in need of assistance from those who know the city. ... while in Middenheim she has discovered her understudy, Bianka Meyer, to be a very talented young singer. She intends to make the girl her protégé and to take her along on her tour of the Empire and beyond.
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Bianka missed last night’s performance, and no one seems to know where she is. Antonia has already sent stage hands to her house but they were unable to discover Bianka’s whereabouts. Then she contacted the watch, who did not take her concerns seriously. So, as a woman of some wealth and little patience, Antonia has turned to private specialists to take an interest in the case – your group of player characters!