Each time one of my cats has become sick over the years, he or she always does it on a day when I can't get him or her to the vet right away.
Little Bit didn't come up to his usual perch for breakfast yesterday, but waited nearby so I thought he was merely upset about something. Later, in the afternoon, he cried out and spat up and became so lethargic I knew something was seriously wrong. I found him sprawled out on the kitchen floor this morning and I thought he was dead. But he stirred and cried out, and fortunately, the vet is open on sundays nowadays so I'm on my way there now.