Who is Arpad Leen from Jailbird and what is their importance?

Arpad Leen is Mrs. Graham's right hand man, obsessively (Starbuck would say religiously) devoted to making sure her will is done. Starbuck's narration also suggests he (Leen) is romantically in love with the rarely glimpsed Mrs. Graham, a circumstance that makes the thematically relevant suggestion that capitalism (in the guise of the intensely capitalistic "Mrs. Graham") can, for some people, come dangerously close to a kind of religious faith.