Usable NPC converstations

Does anyone know where to begain a script on making an NPC talk to you? like i would like for my server to have some around the map just to talk to and find out more infromation about the life they are roleplaying in. Like i would enjoy for each NPC you could go up to and talk to and they would tell you a story about the life you are spose to be roleplaying in. For expample, you talk to a homeless guy and he starts to talk about a zombie apocolpsy that the city has survied and they are trying to re build it, etc etc etc.