Sergei is a computer expert on data mining brought in by Guerrero to pinpoint the other hacker who betrayed 'Casper''s discovery to Nick Chepekian. From the get-go Sergei considers it a monumental task, given the skills and known paranoia of the parties involved, and eventually he announces to Guerrero that, quite simply, it can't be done, and prepares to leave. The contractor, however, stops him dead in his tracks with a hypothetical scenario of what would happen to someone who, say, discovered the identity of someone else holding a world-class secret on Guerrero's dime, and then proceeded to slope off and sell that information to the highest bidder. Sergei suddenly 'recollects' an option he failed to fully explore and - surprise, surprise - Guerrero has the data he needs. Although he's not seen again after this, there's no implication that Guerrero felt the need to go through with his hypothetical scenario.
Sergei is played by Sean Owen Roberts.