In the novel The Secret Adversary, Boris Ivanovitch is one of the members of Kramenin's gang.
Boris is first seen leaving South Audley Mansions with Edward Whittington. Tommy follows them to a tea shop, where he studies Boris' appearance attentively.
Boris is described as being "fair, with a weak, unpleasant face", and Tommy believes that he is either Russian or Polish. He is about fifty years old. His shoulders cringe a little when he talks, and he has small, crafty eyes, which shift all the time.
Boris speaks about Mr Brown to Whittington, saying that he would like to meet him. When Whittington says that Boris may already have met Mr Brown and not known it, Boris says that he sometimes thinks that Mr Brown is "a fable invented by the Inner Ring", and "a bogy" with which they frighten gang members.
Boris later goes to a house in Soho, and attends a gang meeting. He is followed there by Tommy. During the meeting, one of the gang members says that he will guarantee "a reign of terror in Ireland", if the gang can provide him with money. The money is promised, and Boris is told to see to the matter. He asks if the money is to be given via the Irish Americans and Mr Potter, "as usual".
Boris is also asked if he has arranged the details of a loan to an English newspaper, and he says that he thinks he has.
Boris is present when the gang is questioning Tommy, and he is said to know "pretty ways of making people speak".
Boris later calls on Mrs Vandemeyer, while Tuppence is employed as her maid. He gives his name as Count Stepanov, although Mrs Vandemeyer addresses him as Boris. Tuppence finds out from the cook that he comes to the house once in a while.
Boris advises Mrs Vandemeyer to stop seeing Sir James Peel Edgerton. He also expresses the opinion that she would sell her soul for money, and that he sometimes thinks she would betray the gang for money.