Well, at least we have an answer.

Spot has been diagnosed with inoperable stomach cancer. I'm on vacation for a few days right now in Quebec with my cousin (scheduled long before we knew about this), so I'll keep this short, as I am tired and it's very late. I've never been in a position before where the only humane choice I could make for a beloved companion was euthanasia. I'll get to spend one more full day with her when I return before we bring her back to the vet next week to have her put to sleep. Or, to be blunt, put to death. It sucks. I cried many tears on the train yesterday after Derek told me, as did he, and I expect I will cry more, but I can't say I was surprised. I'm trying to stay cheerful before heading north tomorrow to visit with extended family. Time with friends and Marie-France, and some serious Montreal retail therapy today, have both helped. Still, thank you all for your kind support.