6(Who could have sent this letter? Are clues really going to be left behind at each of the fires?...)
4Hey, John...what are you daydreaming about? 
6Nothing, Sir. 
2Your kidding me, a newcomer like you with his head in the clouds during a call!
6Sorry, Sir.
4Well, listen up! We just got information that five people are still trapped in the plant. Save them all and get back here, pronto! You don't have a lot of time before the whole place collapses to the ground! FYI, you need to use the Type B fire extinguisher to put out a fire that can't be put out with the water hose.
6Yes, Sir! (Is this the beginning of the serial arsons? I've got to save them all and find the clue!)