Wolfgang Jager grew up in Iowa---but he's fighting on the "other" side in World War II. And Esther Lange is trapped by her own battles. When Wolfgang is captured and sent to a Wisconsin POW camp, he's relieved---until he's accused of murder! Can faith save him and the woman he loves? 320 pages, softcover from Summerside.
No, Nightingale is not a sequel to Sons of Thunder. You can easily read it as a stand-alone (they are both set in WWII, but that's where the similarity ends. I tried and failed to read SoT, but enjoyed Nightingale).