Years ago, when playing the original God of War on a Playstation 2, I suffered an unusual pang of conscience when I was forced to roast a man alive. Now, keep in mind that the God of War series absolutely revels in ultraviolence and I had just spent hours controlling a man with blades chained to his wrists as he sliced, decapitated, and eye-gouged an army of mythological enemies. But there came a moment where the game settled into a calmer, puzzle-oriented section in which I dragged a caged Athenian soldier around the inside of a temple. Somehow, it was clear, the soldier would help me to progress.

What I didn't understand yet was just how far the game would go to show the dark side of its anti-hero Kratos... but it became obvious as I pushed the caged soldier down a corridor and into a room with two walls of flame jets and a lever. As soon as the soldier entered the chamber, he began to scream directly at me, begging for mercy in a terrified voice. The only way forward was to push the man, cage and all, into a position between the two walls of flame and then pull the lever to roast him alive. Something about the cold-blooded calculus of the sacrifice, coupled with the screams of the doomed prisoner, felt sadistic in a way that the previous violence had not. I had a choice—burn the soldier to death or set the game aside.

Reader, I pulled the lever.

The sickening feeling of that moment has stuck with me since, though it has been hard to say exactly what separated it from a long history of others in my three decades as a gamer. And, really, why should it have bothered me at all? The harm had been entirely virtual, and virtual deeds often have no apparent effect on real-world behavior. For instance, despite years spent perfecting long-distance headshots in games like Deus Ex and Borderlands, I have never even fired a real gun. Yet the discomfort with certain virtual actions remains, and everyone has their own sense of when virtual actions go "too far."

Last month, while in New York City, I had the chance to see Jennifer Haley's provocative play The Nether, which explores the issue of real harm in virtual worlds. The play, first performed in 2013 and opening more recently in New York and London, is a small affair in every way except for the ideas. Running only 75 minutes with no intermission, and with a cast of just five, the taut play isn't much for depth of character, but it does raise an uncomfortable question: should the rape and even murder of small girls be illegal? And if so, where do we draw the line in restricting virtual acts?

The play concerns Morris, an investigator for The Nether—a near-future version of the Internet crossed with virtual reality—who is looking into the Hideaway, a community devoted to letting men have sex with and then axe murder innocent (but entirely virtual) girls. "Papa," the man who runs the Hideaway, has constructed it in the style of a genteel Victorian mansion, all peaceful rooms and gardens and suits and sundresses. He sees nothing wrong with what he has done, and he pushes back against every argument Morris makes for the immorality of the community. Surely, he says, it is better to provide people with virtual outlets for forbidden desires than to have those desires acted on with real children?

But Morris has sent an undercover investigator of her own inside the Hideaway, and the investigator finds himself somewhat seduced by this strangely eerie but beautiful place. He also learns the darker secret of the Hideaway, which is that Papa expects—and eventually demands—that after sex, returning guests "use the axe" to murder the delightful girl at the heart of the Hideaway. The gruesome gesture is intended as a distancing mechanism, reminding visitors that none of this is real and that the avatar of the child will simply walk in again, good as new, from the next room. The lure of the forbidden is so strong that even the investigator is tempted to go further down this path than he ever suspected. After all, none of it is real.

Where the play really gains its power is in the last third, as the identities of the avatars interacting at the Hideaway become blurred, coming into sharp and shocking relief only in the play's final moments. The whole play serves to remind us of how easily we take "avatars" to be reality—even when explicitly and repeatedly told that they are not.

The questions raised by The Nether aren't new, but they do gain power as the visual fidelity of video games and virtual worlds increases. And they force viewers to think more critically about their own views. Where do we draw the dividing line between the moral and the immoral when actions aren't "real"—and where should the law draw its own, more severe line?

Though The Nether has now closed in New York, it continues to play in London until April 25.