The text of this novel of ideas presents itself as a book that has been written as the result of a promise to a dying man. William Porphyry Benham is a man who has lived a life devoted to a complicated, protean idea: "that he had to live life nobly and thoroughly." He has left behind him "half a score of patent files quite distended [with papers] and a writing-table drawer-full," and the novel is by implication what his friend White, who has promised to "see after your book," has produced to acquit himself of the promise, since the papers themselves are "an indigestible aggregation."
Benham is a man of means due to curious circumstances: his mother left his father, a schoolmaster, for a wealthy man named Nolan who died soon thereafter, but not before leaving "about a third of his very large fortune entirely to Mrs. Benham and the rest to her in trust for her son, whom he deemed himself to have injured." His mother subsequently marries a great London surgeon and becomes Lady Marayne; her indiscretion is forgiven and she enjoys a position of privilege.
The bulk of the novel recounts Benham's effort to live nobly, which brings him into conflict with his mother, with his friend Prothero, a schoolboy chum who becomes a Cambridge don, and with his wife, Amanda, a young woman he loves passionately but then leaves behind in England to travel the world (India, Russia, China) in search of wisdom. It is in Johannesburg, South Africa, that Benham is fatally shot while attempting to stop soldiers firing at strikers