Prompted by a violent outburst that threatens his own marriage, successful modern-day author Alex Schulman embarks on a psychological investigation into the roots of the unyielding, toxic rage that has plagued his family line for generations. His search uncovers a dark, decades-old secret from the summer of 1932 involving his maternal grandparents, the brilliant but tyrannical intellectual Sven Stolpe and his elegant wife, Karin. Suffocated by her husband's narcissistic cruelty and emotional abuse, Karin finds a fleeting glimpse of salvation when she crosses paths with a young, empathetic writer named Olof Lagercrantz. The two rapidly plunge into a passionate extramarital affair, but when a pathologically jealous Sven uncovers his wife’s ultimate betrayal, he chooses not to let her go. Instead, he weaponizes the letters documenting Karin's role as a cheating wife, trapping her in a lifelong, psychologically abusive prison that echoes across seventy years and leaves a permanent mark of trauma on their descendants.