When the character enters stealth mode, it allows them to move around the room, stealing any and all items they want without any ramifications (permitted the player stays out of the LOS cone of any NPCs). If an NPC is in a room with the character(s), stealing items without sneaking is impossible even when their back is turned, they will notice the theft. If this occurs in a restricted area or while attempting to steal or lockpick, the NPC will remove you from the area, or a fight will begin. If a Line-of-Sight cone of an NPC intersects the character, the stealth is broken prompting a message stating 'sneaking failed'. Also, the character is allowed to open/close doors and even lockpick doors in this state. a person's bedroom or the legions armory). When a character is in sneak mode, it allows the character to move into restricted areas (i.e. There does not appear to be any benefit to raising sneak above 5. Your sneak skill also reduces the AP cost of entering sneak in combat, becoming 1 AP at level 5 (which is particularly important for making full use of the Guerrilla talent). The higher the character's sneak, the smaller the LOS cone of enemies.
You're perfectly able to sneak without any levels in the ability adding ranks simply makes sneaking easier.
