Mystery Worker is a menial worker for 
Taggart Transcontinental who often dines with 
Eddie Willers in the employee's cafeteria.  Eddie finds him very easy to talk to, and Mystery Worker not-so-subtley leads him on so that Eddie reveals important information about 
Dagny Taggart and 
Taggart Transcontinental.  Eddie tells him which suppliers and contractors Dagny is most dependent on, and with remarkable consistency, those are the next men to mysteriously disappear.
Mystery Worker will turn out to be one of the novel's central characters.
Mystery Worker appears in:
 Section133