Just four new guys, I guess. I could really care less, about that though. What I'm worried about is that the campaign will be WAY to short in co-op. If every player goes to a different "clue" and triggers a flashback, imagine how fast it would be over! As the Rookie, alone, you have to trek miles and miles an your lonesome, and trigger each individual event, but again, each event could be triggered ridiculously fast if each player went after one. I hope this is remedied by the fact that all four (or however many) Rookies need to be at the same clue to trigger the flashback.