Who is Jet, and what does he learn about the cause in the novel, Deacon King Kong?

Jet is the nickname of Jethro Hardman, an undercover police officer disguised as a janitor. Jet is the first black detective to go undercover at the Cause, where he has been working for seven months. Jet has learned that Deems is a low-level dealer who is part of a larger drug network ruled by Joe Peck.