In fact, the GM's Narration is generally the first of the turn. So they do the set up the scene but they also describe the actions of the NPCs first (which could be hostile). Remember that you, as GM do not have to spend a Plot Point on your turn just to narrate the NPC's natural reactions to the PC's actions.
You can spend a Plot Point to "shake things up" or "dish best served cold" (can we just call that "get revenge"? Lol), or glitch dice on THEIR turn. But if security guards would naturally show up (someone tripped the alarm, etc.), they can show up on your Narration without spending a Plot Point.