Li Tai-tai, known as Bittersweet, returns to her hometown of Guilin, China in the 1970s after having lived 15 years in the United States. Her quiet routine is disrupted when a mysterious blue-eyed Chinese man appears on her doorstep and, without explanation, gives her a seemingly ordinary quilt. Hidden inside it, she discovers hundreds of silk pages containing a long, intimate confession written by her unidentified visitor, Hardu. As Bittersweet reads, the narrative shifts between her present life--haunted by memory, loss, and the lingering trauma of her granddaughter Lisa's disappearance--and Hardu's past in early-twentieth century Shanghai, where he grew up as a mixed-race orphan who survived as a ricksha boy, counterfeiter, and petty criminal. The novel intertwines these timelines, gradually revealing that Hardu's story is inextricably connected to Bittersweet's own buried past and the unresolved fate of her long-lost granddaughter. A multi-generational narrative that unfurls in the captivating, textured atmosphere of Shanghai in the mid-twentieth century, Double Thunder is a heart-rending, unforgettable novel.