At the height of its global spread it emerged that the bird disease had likely struck before. The evidence had been hiding in plain sight, in a popular nursery rhyme no less. Ring-a-rosie had been a precedent. An inquiring mind wound through the same rhythmic woods until it came to the blackbirds. Four and twenty, the number of days, or near enough, the virus ran, in those cases where the transformation did not become permanent. The baking of the fever. Sixpence or rye with which to try to buy the time of some overworked physician. Even the amusement of the king struck an uncomfortably familiar chord.