During the proposed joint venture between Lau Security Investments and Wayne Enterprises in The Dark Knight, Lucius Fox begins to suspect that LSI's revenue stream is largely "off the books, maybe even illegal." Bruce Wayne later echoes Fox's suspicions.
So, we know that Bruce/Batman suspects something is up with Lau's finances, but how/when exactly does he link that with Lau being the mob's private banker? I don't remember it being explicitly stated in the film. Is it just one of those things we're supposed to accept, or I am I missing something?