Mr. Middleman is Riff and Torg's boss for a time[1].
Mr. Middleman was recommended to Riff as an employer by someone at Hereti-Corp, but is an outsider player who isn't directly connected to them. He gives Riff and Torg jobs which initially sound illegal but turn out to be completely innocuous. For instance, they assume that giving a customer a "dirt-nap" is an euphemism for killing him, but the customer turns out to be vampire Sam Sein, who is rejuvenated by sleeping in his native soil.
Mr. Middleman has a nephew, Andrew.