I was watching The Fast and the Furious the other evening and the scene came on where a superior tells the undercover protagonist, "You've got 36 hours to crack this bastard". I've also seen similar scenes in other movies and TV shows ("I've got the mayor breathing down my neck", "We've got to catch this guy before he strikes again", etc.) and it got me wondering, are there ever such seemingly arbitrary time constraints placed on investigations in real life? I can understand the urgency of stopping an active serial killer (e.g., the D.C. snipers), but does this sort of thing really happen, or is it just a Hollywood invention to build tension in the plot? When they say, "You've got X amount of time to solve this or we're pulling the plug", what does that even mean, that we're throwing our hands up and quitting or that we're going to start arresting the wrong people just so we can say we did something? I've never understood that.