When Reid, Jackson and Drake are interrogating the culprit in the autopsy room, Drake rolls his sleeves up and the tattoo that he had on his right arm in the previous episode and the next episode is missing.
Ressler's face is scratched in the Molly House by one of the "ladies" on the left side of his face. When they are in front of the Swedish bakery, the scratches are on the right side of his face. At the docks, when Ressler is talking to Reid, the three scratches are back on the right side of his face. This was obviously done so they can be seen from the camera angle.
A cholera epidemic in 1876 is referred to although there was no great epidemic in that year. London suffered four great outbreaks of the disease, all in the mid-19th Century. The first was 1831-1832 followed by 1848-1849, 1853-1854, and 1866. It was during the third outbreak that Dr. John Snow traced the source of the contagion to a water pump and discovered that the deadly illness was waterborne even though the bacillus had not been discovered yet.
Inspector Ressler appears to refer to the victim "Hackett" as "Hackney", but he is actually saying that Hackett comes from the Borough of Hackney.
Inspector Sidney Ressler is scratched on the left side of his face. When outside of the Swedish Bakery, it appears to change to his right but the film is reversed (their watch fobs and pockets are reversed as well).
Flynn knocks on a door using the "Shave and a Haircut" refrain. This didn't become popular until around 1899 but the scene is set in 1889.