Lew Archer's role in The Underground Man is not only that of private investigator. He also serves as a foil for the tumultuous lives of the Broadhurst family. It is almost axiomatic that the detective in a hardboiled crime novel will be static in the way that Archer is, since he is the world-weary figure who has seen it all before and is able to remain unchanged in the midst of the turmoil.
The Underground Man, however, is the sixteenth of eighteen novels to feature Lew Archer and was published twenty-five years after his first appearance in print, in a 1946 story called "Find the Woman." In this story, and in the early novels, the character of Archer is heavily influenced by that of Philip Marlowe, Raymond Chandler's iconic private investigator. By the time The Underground Man was published in 1971, Archer had become less like Marlowe, with fewer wisecracks and more psychological depth and sensitivity. Archer is less cynical than Marlowe and therefore more tragic, since he is more personally affected by the corruption and misery he sees around him. Therefore, although he is a static character within the short timeframe of The Underground Man, Archer is a dynamic character who increases in complexity and vulnerability over the thirty-year timespan of the works in which he features.