A conversation takes place between the player and one NPC, with sometimes added commentary by BlackBird. Plot-relevant conversations usually feature a full-screen portrait of the character and voice-acting for his lines. During a conversation, inventory items can be given to or taken from the player (which is how shopping is implemented), and the actions normally associated to linedef types can be triggered, allowing a limited form of level scripting to take place (for example, talking to a character may be necessary to open a door).
Conversations are stored in binary form in lumps named SCRIPTxy, where xy corresponds to that of the MAPxy map slot. In addition, the conversations stored in SCRIPT00 are valid on every map.