If you open up your Cryptographic Sequencer, you can find three broadcasts from a slightly fuzzy and robotic voice saying seemingly random numbers. These numbers are actually a cipher, numeric representations of the alphabet. Two of the broadcasts are garbage, but the third one says: "9 23 9 12 12 18 5 20 21 18 14 2 1 20 13 1 14" which translates to " I WILL RETURN BATMAN".