Lena Olin, Elodie Bouchez and Greg Grunberg are billed as Special Guest Stars.
Number 47: The frequency that is seen on the radio Sydney uses to send the distress call from the ship, is 447.550.00.
When Tom is looking at the witness protection files one of the files
has number #0174247
The Langley encryption key for the hard drive is 132007479
Amy Acker is added to the main credits with this episode. She takes the place of Elodie Bouchez, who is now credited as a special guest star.
We learn that Tom's wife was called Amanda Grace.
Kelly: You tracked me with the radio.
Sydney: Not really, you're just predictable.
Kelly: A woman in your condition... shouldn't you be resting?
Tour Guide: Aside from the obvious human presence, there are over five thousand surveillance cameras that watch over every inch of the complex and chemical and biological weapons detection sensors that monitor the air quality as well as various other state of the art technologies that, well, if we told you we'd have to kill you.
(Marshall laughs overzealously)
Tour Guide: To this day, no-one has been able to decipher the message. Now, if we move on...
Marshall: I got it! Sorry, it-it just came to me... I-I play a lot of sudoku.
Marshall: (as the alarm goes off) Oh, God! Oh, maybe they found out I can uncover the message, we should run!
Dixon: Take it down a notch, Hamlet.
(Weiss and Marshall wince as they watch Rachel run into the locked door)
Marshall: Err, sorry, I forgot to hit 'Enter'. Okay, now go.
Weiss: And one more thing, next time, just call!
Jack: I'm gonna give you one chance... where are they holding my daughter?
Davenport: What the hell? I don't know what you're talking about.
Jack: Wrong answer.
Devlin: Stop for God's sakes, Jack!