"The Dangerous Age" is a reflective epistolary novel that delves into the emotional and psychological journey of a middle-aged woman who, upon reaching her forties, confronts the societal pressures and personal disillusionments that come with aging. Through a series of candid letters, she shares her experiences of estrangement from her husband, the challenges of maintaining her identity and desires, and her struggle to navigate the expectations placed upon women of her age. The protagonist's introspective correspondence reveals the inner turmoil and liberation that accompany her quest for self-discovery and authenticity in a world that often marginalizes women as they grow older.

The novel follows the story of a literary agent, now retired, who lives a quiet life with his wife in California. Their peace is disrupted when an old postcard from a Danish aristocrat arrives, prompting them to revisit their past. The protagonist begins reading from his old journal, recounting their trip to Denmark years ago, where they became entangled in a mysterious and unsettling affair. The novel explores themes of memory, aging, and the choices that shape one's life.