When a character or monster is brought to 0 hit points, he is considered to be dead, unless he makes a Saving Throw vs. Ray/Poison. If he makes the saving throw he is wounded and unconscious, but can be revived if healed to 1 hp.
A player character can spend a FATE CHIP on himself or any henchman or hireling (but not allies or other PC’s) to re-roll any failed death saving throw. If that fails, he may spend all his remaining chips (if he has at least 1) for one more chance.
If healing magic brings the character to 1 hp or above, he’s back in the action.