When Elvira Cummings (Alison Jantzie), a young opera singer, is poisoned during a rehearsal of La bohème, Detective Murdoch (Yannick Bisson) suspects the intended victim was Madame Rosa Hamilton (Measha Brueggergosman), the diva who stormed off stage moments before her protégé collapsed. Showing her thoroughness and skill, Dr. Grace's (Georgina Reilly) autopsy brings her to the same conclusion as Murdoch: the aspiring soprano was killed by a fast-acting poison, likely slipped into her prop glass by one of the other on-stage performers. A serious opera aficionado, Inspector Thomas Brackenreid (Thomas Craig) takes a personal interest in the crime, and the famed and flirtatious soprano, inflaming the jealousy of his wife Margaret (Arwen Humphreys). Further investigation into the opera company uncovers almost unanimous disdain for Rosa, and a rumoured love triangle between Rosa, her longtime lover, tenor Carlo Corsi (Paulino Nunes), and the dead singer. As Murdoch, Brackenreid and Constable George Crabtree (Jonny Harris) delve for answers, the dramatic behind the scenes machinations reach operatic heights.