YMMV / Endeavour S 1 E 02 Fugue

• Complete Monster: The Opera Phantom, Mason Gull, is a musical prodigy institutionalized for killing his own mother when he was fifteen. Getting released by faking being cured, to prove his genius to the world and take revenge for his imprisonment, the Phantom embarked on a twisted killing spree, basing his murders on deaths from famous operas to create his own treble clef, EGBDF, leaving clues and taunts to challenge the police. He strangled Evelyn Balfour, poisoned Grace Madison with devil's snare, and chained Ben Nimno up underground before bricking up the wall, leaving him to slowly die of dehydration. Kidnapping 6-year-old Debbie Snow, the Phantom challenged Morse to find the girl before morning leaving several riddles, as a distraction for him to use an acid trap to kill Dr. Daniel Cronyn, his former therapist who he'd been impersonating. Holding Inspector Fred Thursday at knifepoint, the Phantom planned to kill him as a stand-in for the officer who arrested him, then surrender to bask in his new found fame, admitting that he planned in ten years to fake being cured again, following which he intended to commit another killing spree just to ensure that his name would always be remembered.