'American Horror Story'

Sister Mary Eunice has a word with Frank. (FX / November 29, 2012)

Who knew that the devil actually had a plan before inhabiting the body of Sister Mary Eunice?

Unless that plan included slashing the throats of patients and investigators, and trying to seduce Dr. Arden, it seemed like the spirit was just winging it.

In reality, every move she's made so far has been calculated. The demon wants to run Briarcliff. Last week, her actions led to Sister Jude packing her bags. This week, she exercised her control over Dr. Arden.

After Grace is found bleeding, with her girl parts "scooped out," Sister Mary Eunice blames Arden for the failed sterilization attempt. Always up for a chance to argue using gaudy vocabulary, Arden retaliates.

"I performed no sterilization, Sister," Arden insists. "I demand to be spoken to with at least a modicum of respect."

No stranger to hitting women (or degrading them), Arden slaps Mary Eunice across the face. At least he managed not to call her a whore, so there's that for a sign of progress.

"You touch me again ... you will die," says the demon.

The slap-happy Arden goes in for another thrust to prove his dominance. It proves to be the wrong move as Mary Eunice sends Arden flying across the room.

"I hope that quantifies the chain of command, Arthur," she says.

Touched by an angel

After a patient named Miles tries to kill himself by sawing his arms off, he calls for the Angel of Death to take him away.

The angel, played by Frances Conroy (older Moira in season one), does just that and draws the attention of Sister Mary Eunice.

Mary Eunice confronts the angel and tells her to leave. The possessed nun must not like people stealing her kills. Somebody tell her this isn't "Call of Duty" and she's not earning points for each death.

The angel points out that Mary Eunice, that is the real Mary Eunice, wants to be killed and freed from the demon's grip.

"Now leave this place," says Mary Eunice. "You're not wanted here."

"The girl you've taken hostage sings to me," replies the angel.

"We have work left to do," says the possessed nun.

The angel promises her "dark cousin" the two entities will meet again.

Keeping a busy schedule, the angel next appears in Dr. Thredson's basement where Lana is being raped by the doctor.

As the angel appears, black wings unfolded and lips ready, Lana tells the angel she doesn't want to die just yet. Too bad Lana doesn't get to make that decision since she's being held captive by a serial killer.