Sylas wields an ancient power to sense and siphon away pain from others, but struggles with the moral ambiguity of his abilities, leading him to question his purpose as a Syphon. Livia, his partner and a neuroscientist, explores the impact of emotional trauma and the ethics of healing from it. Together, they unravel secrets of the power that will forever change their relationship. Meanwhile, deep in the Amazon, an ancient threat re-emerges with plans to unleash a terrible darkness.