After solving three of the four Further Investigation metas (i.e., beyond the Poirot meta), solvers were invited to schedule a final visit with Poirot to crack this case and determine who was behind everything all along. Poirot then helped the teams use the 4 Further Investigation meta answers and the following questions to find the mysterious mastermind:
You can confirm your guess of who the mastermind is in the answer checker (call in first name only), and then view the Solution to read the script of the final story interaction of the hunt.