"Killer Chat" is the 11th episode of the third season of the American television show Numb3rs. In the episode, Federal Bureau of Investigation (FBI) agents investigate the murders of several child molesters while a pair of mathematicians prepare to say goodbye to a friend. Stories about child molesters and his own experiences as a parent inspired series writer Don McGill to write the episode."Killer Chat" also serves as the final episode of series regular Peter MacNicol before his stint on 24.