So, I got home tonight, opened the mail, and our monthly mortgage statement suggests that a payment of $20,020.71 was made on our mortgage during Thanksgiving week - as well as our ordinary, much much smaller monthly payment. The amount of the mystery payment reduced our mortgage balance by about 40 percent. I figured, hmm, interesting error, probably due to the credit union recently outsourcing mortgage recordkeeping to another company. But I also just checked our online credit union account, and the payment appears there too. Either a large error has been made, the S.O. is keeping a large secret from me, or some anonymous donor is hard at work. I'm guessing #1. I can't verify #2 until S.O. gets home from his haircut, and if it wasn't him, we can't verify #1 or #3 with the credit union until business hours resume tomorrow.