Ye Zhen suffers from "Rainstorm Syndrome" whenever it rains, her memories return to a year ago, to the day she made a promise with a certain man. In her search for the truth behind those lost memories, she becomes entangled with Jiang An, the mysterious bookstore owner—aloof, distant, full of lies and secrets, yet always watching over her. His familiar face leaves her deeply unsettled. But who is he, really? An insider? A protector? Or the mastermind behind it all?