This passage shows that while Mulberry is carrying out a scheme to get closer to Kate, he is also carrying out a scheme to convince Frederick that he (Mulberry) is acting in Frederick’s interests. The second part of that scheme (which involves lying to Frederick) underlines the novel’s ideas about the illogic of using one’s own self-interest as the primary basis of one’s decisions. In this case, Mulberry makes it clear that he is untrustworthy and willing to betray even those close to him, including Frederick. The novel implicitly asks, if Mulberry is willing to betray his closest friends, what will stop others from betraying him?