dismallyOriented

Yes, the plate! You can treat it as the microwave equivalent of putting a pyrex on a stovetop (also something wife and I did once, on accident), or leaving an empty dish in a running oven for too long. My guess is that without the recommended 2-3 other tenders, all the energy from the microwave ended up concentrated in and heating up the plate, until it cracked from thermal shock. Damn shame, there were 13 seconds left on the timer.

....not my brightest moment