As technology and scientific understanding advance, religion may find itself going on the offensive for the hearts and souls of man. And we are beginning to suspect that the most dangerous agents in that battle will be the nuns. Yes, many holy sisters are out tending to the sick and poor, but we wondered if some weren't packing more than rulers between those robes. We looked at science fiction's nuns and found that beneath those pacific exteriors lurk disturbing experiments, wanton slaughter, and shocking deceptions. Possible spoilers ahead.

Evangeline: Following a massacre at an orphanage, the Catholic Church recruits a young survivor, Evangeline, to be its avenging angel. Armed with big guns and slinky outfits, Evangeline hunts down nun killers, rogue geneticists, and anyone else who defies the pope's commands. Why we won't trust her: Evangeline keeps her vows to the Church a secret, masquerading as Countess di Christina. On top of that, she's an unthinking and remorseless killer, blindly obeying the orders of her mentor, Cardinal Szn.

The Sisters of St. Hilda's: In Charles Stross' "Down on the Farm," the mechanized Sisters of St. Hilda of Gratham's Home For Disgruntled Waif and Strays tend to agents of the Laundry who are, as they say, "differently sane." They keep careful watch over the patients in the secure wing and attend to the strangely tweaky Funny Farm administrators. Why we won't trust them: Each Sister is connected to and controlled by the Matron, a machine-bound entity who is none too pleased to be in the service of the Laundry. And the Sisters have been known to lock up agents who aren't patients. We don't believe for a second that it's a coincidence.

The Sisters of Plenitude: Another order of nursemaids, the feline-faced Sisters run the top hospital on Doctor Who's New Earth. Through careful study, they have developed advanced medical technology that allows them to cure every disease known to man. Why we won't trust them: That medical technology comes at a chilling price. Those Catkind angels of mercy farmed human clones for thousands of years and infected them with each one of those diseases for study. Even if that doesn't ping your creep-o-meter, consider that once ever few millennia, one of those suckers might get loose and start a plague. Sister Carlotta: Carlotta is a veritable fairy godmother to Bean. First she sends him off to Battle School, where he befriends the likes of Ender Wiggin and begins a promising military career. Then she finds his biological parents and reveals that his best bud Nikolai Delphiki is his genetic brother. And all the while, she does her best to protect Bean from the machinations of Achilles. Why we won't trust her: She waited until after her death to inform Bean that he possessed the genetic modification Anton's Key, which accounted for his extreme intelligence, but would also result in his premature death. We know she was only trying to protect the kid, but it still would have been nice to know that he shouldn't go planning for retirement.

Mary Malone: It's 2012, and you're a soldier for the fascist government of mainland Europe. A nun appears to tend to a dying enemy combatant in your care, and, because you're not a total barbarian, you let her in. Why we won't trust her: That's no nun; it's "Bloody Mary" Malone, from Garth Ennis' comic of the same name, a rebel commando with a penchant for donning habits on particularly splatter-filled missions. It's a handy rouse, but she may just like the way they look covered in bullet holes and blood.

Maya Herrera: After turning her awesome death power on her brother's wedding – killing off guests, the wedding party, and her faithless future sister-in-law – Heroes' Maya enters a convent, hoping God will help her overcome her tendency for mass killings. Why we won't trust her: Actually, this has nothing to do with trust. We're just steering clear of Maya in general.

Channon Yarrow: Overwrought from dealing with her crazed boss Spider Jerusalem and her boyfriend's transformation into a cloud of nanomachines, Channon signs up with the Brides of Christ – Fred Christ, that is. There she is free from the stresses of the outside world and receives regular ministerings from the half-alien love guru. Why we won't trust her: Channon knew full well what Fred was capable of when she joined up. But once she defects back to Spider (claiming that "The sex was lousy"), she holds special contempt for the Transient leader, coldly cursing him during one of Spider's more physical interrogations, and even getting a few shots in herself. Granted Fred deserved it, but we're still not letting Channon join our alien sex cult.