A natural one, and the scene ends nothing like you were playing it. Now outstanding roleplay earns your character a die of fate: one roll can be taken back.
Die of fate — granted for a scene of the highest rank, spent to reroll a roll of your own
Quietly — everyone else in the scene simply sees your die still in the air
Critical failure — can be rerolled too, and that is the most common reason to spend the die
An honest d20 — the faces show what came up, with the stat the action is judged by right beside them
Dominance — when the gap in skill is too wide, the card says it plainly: that decided it, not the roll
The game master sets it all: the score that earns the die, how many rerolls per roll and per scene, how many seconds you get to decide.