This morning I got up and walked into the livingroom, finding Nano (looking smug) on the sofa with an empty chocolate-bar wrapper between her paws. I thought I had stored the bar away, 'cause I always do that. Not last night, unfortunately, so when I saw her looking at me and the leftovers of the wrapper, I freaked out a little. A call to the vet calmed me down (kudos to the other person on the line), as we calculated how much she had and what type. She had about half of the 'minimal toxic (not lethal)' dose, the vet said.
The vet told me to keep an eye on Nano, feed her some extra to dilute the chocolate somewhat and check to see if Nano drank enough. She drank a lot today, and spent some time on the sofa making small whining noises (I suspect a tummy ache) and seems otherwise fine.
This of course happens right after boyfriend suggested poisoning the dog in my Nanowrimo-novel.