Orchid House Cipher
S16E02: The Yellow Dust
The yellow dust was pine pollen, impossible inside a filtered tropical house in winter. Tess found the same pollen in Saye's lungs, but not enough to kill him. Beneath it hid crystals from monkshood root. Saye had inhaled powdered toxin through the greenhouse mist. The system normally used liquid fertilizer. Someone fitted a dry-pollen injector to the humidifier, allowing poison to enter after the door locked.