Steel yourself for another round of ...whatever it is that Valve's doing with Portal PC, as a second mystery update for the game just arrived via Steam. The only clue note:

# Added valuable asset retrieval

The first mystery update, released Monday, added various radio transmissions to the 2007 game--leading to Morse code, hidden images and even a secret Apeture Science BBS--all the while prompting speculation that a Portal 2 and/or Half-Life 2: Episode Three announcement is imminent.

Update: Gamers are reporting that the ending to the game has been changed. A video has been uploaded, which shows the altered sequence. What used to fade to black now takes very interesting twist using one of the soundbytes uncovered in the original content patch from Monday.