June, 1976. Western Europe is caught in the grips of a relentless and sweltering heatwave. In London, the summer marks a milestone of a different kind for Edie: a decade married to the love of her life, and their first child on the way. But on the night that she plans to tell Joe their news, he doesn't come home. Fearing the worst, Edie scours the city for her missing husband, and eventually she unearths a clue: Joe's wedding ring, alongside a note urging her towards Paris. Using her heart as a compass, Edie sets off on a journey that takes her across Europe, following a trail that promises to unlock the mystery and lead her to Joe. As tensions rise and temperatures soar, Edie draws closer to the truth - but unravelling the past comes at a cost. When the heatwave finally breaks, will it take Edie down with it?