First time D&D 5e GM here.
At the beginning of my campaign, an NPC will try to send the party on a covert operation. I'm giving one of the characters a special role and backstory: He's that NPC's "mole", and knows special details about the mission, which he is supposed to spill when the time is right.
I'm ok with the characters finding out "too early" about those details (I don't want to railroad), especially if the mole behaves in an unusual way, makes seemingly contradictory decisions or pulls secret knowledge out of his hat. But I'm seeking advice whether the other players can know about his backstory beforehand? What are the most important points in favour or against doing so?
Some thoughts I have had so far, although I lack experience to weight them:
- The players really enjoy learning about each others' characters' backstories.
- It might be hard for the player to keep his secret all the time.
- It takes an interesting surprise out of the story
- It's hard for the other players not to meta-game, i.e. to let their characters not know what the players know.
(Related question: How to discuss information only my character knows with the DM during the game?)