How to move an NPC behind the scene?

Let's say I have a House scene and a Town scene. Player and NPC stay in the house scene. When it's 09.00 AM, NPC must move into a specific position in a town scene and probably arrive at that specific point at 10.00 AM. That means the NPC following some "path" along with two scenes between 9 AM and 10 AM. My question is how do I know the NPC exact position in the town scene even when the player is still on the house scene? So when the player goes to the town scene around 09.30 AM, the player can see the NPC still walking into their specific position. I have a persistent scene and load/unload other scenes additively when the player moving between scenes. I don't know how to move the NPC "behind the scene". I hope my question is clear enough because English is not my native language.