After weeks and weeks of speculation on what exactly could be Bailey's tragedy - and the cause of her narration replacing Meredith's for an episode (Lay Your Hands on Me), it seems that some people at the ABC Message Boards have finally unearthed the truth behind the tragedy. Read with caution, cuz it ain't pretty. (FYI, you can change your vote in the poll to the right after reading this, if you do so choose.)

dappybee says...
Either Bailey's husband or son dies when a book shelf falls on him. That is why she will narrate 1 episode.
dolphcharge says...
Well, according to the sides, it is Tuck (her son) who gets crushed by the bookshelf... How do we know someone dies?
LILBAIL3Y says...
I read that Callie saves Bailey's son and she is suppose to offer Callie her job back, but I don't know how true that part is.
icankillyouwithmybrain says...
It makes sense that Callie is the one who saves him because I read that Tuck breaks like 3 ribs. Bailey might offer it back in desperation, thinking "I should have been home", or out of guilt. But I doubt Callie would take it back or that Bailey would REALLY want to give it up.

UPDATE: Here's Michael Ausiello's Vodcast, where he's got a self-proclaimed "graphic re-enactment" of Bailey's tragedy. It's the whole thing, so you'll get some scoop on your other favorite shows, such as House or Supernatural as well! Enjoy.