In Joseph Conrad's Heart of Darkness, Marlow is put up on a pedestal by the brickmaker (the "Young Agent"), a "gentlemanly" sort of man who the other agents don't associate with—thinking him a spy for the Manager. It would seem that he not only keeps to himself, but that he had designs on one day being the "Assistant Manager."
The term "gang of virtue" is the brickmaker's way of referring to a "new generation of leadership" selected by the Company. He erroneously thinks, because Marlow's affluent aunt recommended him for the job, that Kurtz and Marlow have been hand-picked by the Company to lead the way into the colony's next wave of financial success.
Marlow has asked the brickmaker who, exactly, Kurtz really is:
`The chief of the Inner Station...He is a prodigy...He is an emissary of pity and science and progress, and devil knows what else. We want,' he began to declaim suddenly, `for the guidance of the cause intrusted to us by Europe, so to speak, higher intelligence, wide sympathies, a singleness of purpose...
'...and so HE comes here, a special being...Today he is chief of the best station, next year he will be assistant-manager, two years more and . . . but I dare-say you know what he will be in two years' time. You are of the new gang--the gang of virtue. The same people who sent him specially also recommended you...
`When Mr. Kurtz,' I continued, severely, `is General Manager, you won't have the opportunity.'
The brickmaker describes Kurtz as if he is some kind of "child-genius," a brilliant member of a new generation of "leadership." (He will not be the only person on Marlow's trip to look at Kurtz—or at least the mythology surrounding him—this way.) The brickmaker alludes to the potential of the other agents (including himself), noting that they are looking to Europe for guidance—for assistance to also be great if only given the chance.
Because Marlow's aunt helped him to get this job, the brickmaker sees Marlow as part of this new generation of "super-management." Marlow is humorously surprised—he is nothing more than a steamboat captain—and wants to be nothing more than he is.
The brickmaker prognosticates that Kurtz will be the Assistant Manager in time, and soon after, the General Manager of the entire project. Marlow realizes that the brickmaker had hoped to have that position himself, until Kurtz showed up and demonstrated an amazing ability to export enormous amounts of ivory. And so, the legend regarding Kurtz grows—even around Marlow.
Marlow, ironically, has nothing in common with Kurtz. The madness that infects the Lower Station has spread deep into the Congo and has Kurtz in its grasp. Marlow, however, is not a "Company man," and has no desire to act like the others...with their careless disregard for human life and their worship of ivory. However, the brickmaker has his own ideas and the reader gets the sense that nothing Marlow might tell him will change his mind.
The "gang of virtue" refers to the "forward-thinking" management candidates the brickmaker sees in Kurtz and Marlow. (There may also be a sense of "the great white hope"—an upper-echelon of white men that will make the Congo colony more successful than anyone could ever have imagined. This is, of course, a totally false supposition on the part of the brickmaker.)