Will Oliver

Hey all, we had a game of Urami vs Nightmare and weren't sure in the timing for these two. Example, insidious madness attacks with willpower based melee, succeeds and does damage. The target has Vengeance so it's able to do 1 damage to attacker after resolving. The nightmare has feed on fear which can heal one after a failed willpower duel by target. So does the attacker take a damage but then immediately heal it, or is the timing/order different then that?