This is Jules Delaunay's The Plague In Rome (131 x 176 cm) which was a huge hit at the 1869 Paris Salon. Critics at the time likened it to an operatic production. As described by Robert Rosenblum (see previous post), this work is a blend of the historical and supernatural. It illustrates a narrative from The Golden Legend (a 13th Century compilation) that tells the story of how, during the Roman plague of 680AD, a good angel commanded the bad angel to strike the doors of the godless with a spear, the number of knocks determining how many deaths there should be in the home.
Rosenblum explains that epidemics such as cholera were still recurrent in 19th Century France and, as is often the case with human disasters, a religious explanation of sinful behaviour could easily be provided.