Yarn v3 is an NPC dialogue/Interactive Story plugin for Unity 5.x and above.
Note: You need Unity 5.x Basic (Free) or Pro.
Full demo showing plugin capability included.
Please note that to keep that price of the plugin at a minimum there will be email support only and a full refund will have to suffice in some circumstances. You also need at least some coding experience in C# to make full use of the plugin. By purchasing the plugin you show that you accept these statements.