airdate: January 26, 2010
written by: Gil Grant, Matt Pyken
directed by: David Barrett

• Dom is missing, and the episode leaves no definitive conclusion. Is he dead, or alive?
  
  
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• This is the first episode in which Barrett Foa (Eric Beal) is listed as a regular cast member, and Adam Jamal Craig (Dominic Vail) is listed as a recurring character.

• The clips of Hetty (Linda Hunt) and Kensi (Daniela Ruah) in the title sequence are changed.
  
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• Onahoua Rodriguez (Claudia Taro)
  
• Maurice Compte (Rafael Taro)
  
• Parry Shen (Ty)
  
• Gonzalo Menendez (Jose Caro)
• Matthew Grant Godbey (LAPD Detective)
  

• DISCUSSION THREAD
  
  
• DISCUSSION THREAD

• LD50 - A crime scene poses a national security risk when the LA team discovers the location was used to create a deadly toxin which is now missing.