Last week’s The Vampire Diaries, “Katerina,” dealt us a heavy blow of exposition, but it was far more lively and interesting than boring ol’ “Memory Lane.” There was so much going on here that we better just dig right in.

“The” Curse

First, a bit of housekeeping: every time someone says “the curse,” you might think that they are talking about one curse, but you are wrong. Even saying “the sun and the moon curse” is still conflating ideas. From now on there are three (3!) curses : 1) the sun curse, aka the curse that restricts vampires to the night; 2) the moon curse that turns werewolves under the full moon; and 3) the Petrova curse. Speak of the devil . . .