Charlie Schneider, a respected New York psychiatrist, has a problem. His latest patient, Rupert Scott, is a young pianist who has been in and out of state institutions for most of his life. Everyone agrees that Rupert is a once-in-a-century talent, but he hallucinates—he sees sounds as beautiful but often terrifying visions of light—and he’s haunted by a childhood trauma that threatens to shut him down every time he plays. 

Hallucinations are typically treated with drugs, but Rupert’s musical ability is somehow bound to his visions—and Charlie fears that snuffing out the light will end his patient’s only chance for an exceptional life. Unsure how to proceed, Charlie consults with Baxter, a legendary experimental psychiatrist now at the end of an illustrious life. He suggests that Charlie transcend the ordinary doctor-patient relationship and attempt to experience the world as Rupert does. 

Baxter leads him through mind-bending experiences at his Institute of Experimental Neuroscience and Psychiatry, and Charlie soon finds his own life spiraling out of control. Through double-decker psychiatric sessions—Baxter with Charlie, Charlie with Rupert—Charlie begins to suspect that a childhood trauma of his own lurks below his consciousness. And there’s a more immediate problem: by entering Rupert’s world, Charlie finds himself courting a madness that may consume them both.