As the player enters a location as part of a quest I want the quest objects guard to intercept the player and test to see if the player is carrying an item to make sure player is not an assassin etc. The player enters a location and after traversing a corridor the guard will block the way and pull the player into conversation. If the player has a certain item the guard will give him a warning and let him pass. If the player has no such item then all items of food, armour etc in the room will not be available to the player who will be a thief if he takes them. The guards will allow the player to move around but will follow him closely.

This sounds complex to me but to someone else may be very simple.

1. How to get an NPC to pull player into conversation and not let player pass.
2. How to make all items not available to player, but available if he has a certain item in possession.

You need a find or ambush package for the guard, which targets the player and fires when the player is in the cell and a certain quest stage is set.

Ahh, you know what? I'm bad at explaining these things.

I'll leave it to someone else.

It's not hard to do, at least.