Surge.

When Revealed: If Mîm’s objective side is faceup, add 1 progress token to Mîm if this is the first copy of Captive Son revealed this round. Then, if the number of progress tokens on Mîm is equal to or greater than his flip him.

It was the capture of his son and their threat to torture him that led Mîm to his treachery.
–The Children of Húrin