On Salem Season 2 Episode 7, Mary is determined to take down Countess Marburg and resurrects Increase to help her in her mission. He tells Mary he needs to go digging around before he can tell her what she needs to know. Mary decides to put together a dinner party and invites Countess Marburg, and others, so Increase can do some digging around in Countess Marburg's home.
At the dinner it's clear the Countess knows something is going on, but she doesn't let on she's aware of ulterior motives. Countess Marburg even states what she's going to do to each person when she takes over and plans to kill anyone who is basically a free thinker and who has strong opinions because it's those people who you need to watch out for. At the end of dinner, Mary's son comes into the room and immediately the Countess sees this is going to be her solution to get her "dark lord" back and plans to have Mercy steal the boy.
Meanwhile, Dr. Wainwright has a live patient with the plague and before the patient dies, the Doctor decides to do some literal digging around. He opens up the man and his organs are liquefied and there is black bile coming out of the patient and sinks down to the floor to parts unknown.