On an alternative Earth, the highest mountain is not Everest but rather The Wheel, which "sits alone, thousands of kilometres from any other landmass, half way between Tasmania and Antarctica, in the midst of the Southern Ocean".

The Wheel dwarfs all other mountains. At 25,000 metres, it reaches through the troposphere and climbs thirteen kilometres into the stratosphere, "a part of the atmosphere that is entirely alien to the realm in which humanity exists". The summit of The Wheel, known as The Hand of God, has only been reached once, in 1974, by multi-billionaire mountaineer, Walt Richman. Unsuccessful attempts had already claimed the lives of Mallory and Hillary. Richman spent millions ensuring his attempt was successful, with teams of climbers creating supply chains and establishing a series of huts. Once he had reached the summit, Richman had everything dismantled, so that he alone has been the only man on Earth to conquer The Wheel.

Now in his 70s, Richman has used his vast wealth to buy Theodolite Isle, "the Wheel's sole companion in all the wilds of the southern sea", and built his dream home, carved out of the mountain that dominates the island. Richman's architect, Richard Gausse, died during construction and when Richman holds a private celebration for those involved in the project, he invites Gausse's daughter, Rita. Estranged from her father, she has a chequered, scandalous past and an unusual talent, which is Richman's true motivation for the invitation. Combining elements of Agatha Christie's And Then There Were None with John Carpenter's The Thing, The Rich Man's House is a horrifying, graphically violent thriller.

McGahan intersperses his narrative with historical journals, newspaper reports and extracts from Rita's book to create a convincing alternative history of mountaineering and to establish the backstories of his characters. Walt Richman is a remarkable creation, a flawed hero and a narcissistic liar whose hubris inevitably brings nemesis. However, the repeated interruption of the narrative line, at times, destroys the extraordinary tension that the main story line generates. McGahan understood there were flaws in his novel. In a poignant foreword he admits that "this is not quite the book it would have been had cancer not intervened". Readers will not only mourns the loss of McGahan but also the novel this might have been.