This one falls squarely into the category of "Oh Crap!" Seems that we had someone over working on the roof. Ya gotta love how builders do crappy jobs knowing that by the time you figure out that the nail holes in the roof they've left leak they'll be long gone. So we had nail holes that over the centuries have started to leak. Lovely. So the fix-it guy put a pan into the attic in case it rained, but didn't remove it. So, your's truly wandered into the roof to retrieve said kitchen pan...
Yup - you really do fall through quickly if your foot slips off the beam. Imagine my foot dangling through and you get the picture as it was all of a sudden like. If it didn't hurt so bad it would have been funny...well, it was funny all the same.