Author, poet, critic, and suffragist Mary Amelia St. Clair was a contemporary of and acquainted with Henry James, Thomas Hardy, Ford Madox Ford, T.S. Eliot, Ezra Pound, and Rebecca West, among others. She served as an ambulance driver in World War I, and produced poetry and fiction based on it.

The Tree of Heaven draws upon Sinclair's experiences in the war. Concerned with the Harrisoon family, it follows the three children, Michael, Nicky, and Dorothy, as they grow up in the 1900s and face the war as young adults. Dorothy hosts a sufragette meeting that lands her in jail, then trains with the Red Cross and joins an ambulance unit in Belgium. Michael is a poet involved with avant-garde artists, embracing pacifism and resisting family pressure to join up. Nicky is an engineer who enlists early and invents an early prototype of the tank.

The novel examines the ideals of the suffrage movement, the spiritual uplift of the war, and the personal cost both could extract from those involved.