In 1899, 17-year-old Emma Rauschenbach, one of Switzerland’s wealthiest heiresses, fell in love with Carl Jung, a penniless Irrenarzt, or doctor of the insane, then the least respected of all medical disciplines. Emma’s parents encouraged the love match. They wanted their daughter to be happy. She would bring more than enough money to the marriage, and despite Carl’s peasant background and inauspicious career, he was keenly intelligent and hard-working. There was also the allure of having a doctor in the family – one who could attend to the increasingly debilitating symptoms of Emma’s father’s shameful syphilis, contracted during a rare “transgression” while on business in Budapest.

None of them could have foreseen just how far this young doctor’s ambition would take him: from his beginnings as a “lowly assistant physician” to one of the leading lights in the newly fashionable field of psychoanalysis; the man initially chosen by Freud himself to be his professional heir; and one whose expertise would be sought by some of the wealthiest and most important figures of the age.

Although a virgin when he married, as Carl’s professional proficiency grew so did his sexual prowess

Catrine Clay takes the title of her biography of the Jungs’ partnership from Carl’s 1925 paper, Marriage as a Psychological Relationship, in which he argues that one’s relationship with one’s parents – bad or good – has a direct influence on one’s choice of marital partner. A typical union, he argues, often consists of one party who experienced a positive relationship with their parents, the other the opposite, “burdened with hereditary traits that are sometimes very difficult to reconcile”. Managing the latter’s delicate psychology can be a notable drain on the former, who, as a consequence, “can easily lose themselves in such a labyrinthine nature, sometimes in not a very agreeable way, since their sole occupation then consists in tracking the other through all the twists and turns of his character”. As Clay’s vibrant and engrossing study illustrates, Carl could easily have been describing his own marriage, specifically the fate of his intelligent and highly capable wife as she struggled with the caprices of her precociously gifted, but neurotic and infamously mercurial husband.

If this seems today like an ill-advised blurring of the boundaries between the professional and the personal, Clay reminds us that the early days of psychoanalysis were rife with such confusion. Plenty of first-hand experience made it into theoretical texts, and analysts interpreted not only their own dreams but also those of their nearest and dearest. Affairs between analysts and analysands were not uncommon; and, enamoured with their own cures, analysands frequently went on to train as analysts in their own right. Even so, Carl and Emma’s story provides us with more scandal than most: a man who pursued a career in psychiatry because it spoke to his own neuroses; a wife whose fortune bought him professional freedom; a couple who each cultivated a close friendship with Freud – Emma often seeking the Viennese doctor’s advice when it came to the problems in her and Carl’s relationship – the now notorious parting of ways between Carl and his surrogate father/mentor; Emma’s late career as an analyst; and then there were Carl’s affairs, two in particular with former patients turned analysts: Sabina Spielrein and Toni Wolff.

Although a virgin when he married, as Carl’s professional proficiency grew so did his sexual prowess. David Cronenberg’s 2011 film A Dangerous Method offers a rather salacious dramatisation of Jung’s liaison with Spielrein, casting Michael Fassbender (then of Shame fame) as the irresistible Swiss doctor. Even more shocking, however, was the relationship with Wolff: tolerated by Emma for 30 years, it was a brazen ménage à trois, not only personal but professional, with the three astonishingly passing patients back and forth between them.

Despite such provocative material, and in noted contrast to Cronenberg’s treatment, Clay resists any urge to embellish, diligently sticking to the facts and presenting even the spiciest of details with admirable restraint. Like Ariadne with her ball of thread, Clay navigates the maze-like story with perspicacity and ease. She uses psychoanalytic jargon sparingly, and only to throw illumination on the lives of her subjects. Celebrated above all is Emma’s fortitude. She is the epitome of the adage “behind every great man there’s a great woman”, and, although the Jungs’ story is uniquely intriguing, the structure of their relationship is all too familiar: the genius husband who strays, the wife who graciously holds the home together, brings up the children, plays hostess and helpmeet, putting her own ambition on hold.

Too long overlooked, Emma’s legacy mimicked her life – Labyrinths is the first mainstream publication to recognise both the value of her contributions as a practitioner of analytical psychology, but more importantly to acknowledge the integral role she played in the discipline’s development. As Clay astutely demonstrates, Jungian theory was a direct product of the specifics of this marriage: “The world would not have had the Carl Jung it knew without Emma Jung, steady in the background.” It’s a gripping story of two talented individuals; their fascinating, often troubled, but ultimately enduring partnership; and how together they shaped the brave new world of psychoanalysis.

Labyrinths is published by William Collins (£20). Click here to buy it for £16.40