Wow! that was very good, and a bit frightening! I like how you put Ring Around The Rosy in it. Very creative- good thing all that isn't around now!

I'm a sucker for Black Death stories, so I had to check this out. I liked the hints of scenes, sort of like teasers. I thought it worked very well. I also like how you (mostly) begin these small scenes with "Caroline!" or even "Katherine!" The repetition made me feel like I was daydreaming with the last segment and the new segment demanded that I pay attention (in a good way! lol).

I almost like it better that you didn't give any specifics. Her mother doesn't have a name, they don't live on a specific London street (like Fleet or near the Thames). I think either you should give everything names or leave everyone but Caroline nameless, such as the Lord Montague and Katherine. I think that would give it an oddly chilling effect.

As far as historical accuracy goes, I'm not sure if you set the Plague in 1338 as indicated or if that was just recalling when the protagonist was younger. The plague hit London in 1348 and the initial outbreak lasted til 1350s, though there were subsequent outbreaks for centuries. I'm not sure if the rhyme is from that time period (there's some speculation it came during the 1665 one), but it works because you don't have any character directly saying it. The posies were a nice touch, since usually people carried flowers or spices to hold to their noses as they walked past all the death.

Nice job!
*faery tragedy

I swear the rhyme is 'Ring a ring of roses a pocket of poises a tissue a tissue we all fall down'
AND
I SWEAR the plague was later than that . . . because it died out after the great fire of london in 16 becuase all the rats were burned . . . maybe I'm wrong . . .