You steel yourself, repressing the certainty that this cannot possibly be a good idea. With one more deep breath, you reach a (only slight shaking) hand into the darkness. For a moment your fingers feel, thankfully, only cold stone. Then, you brush against something!
You draw out the item, and are pleasantly surprised to find a small key. It’s oddly warm to the touch. You look back up to the portrait and are startled to find it returned to its original state. The only evidence of the damage of the devilish flames is a slight darkening around the eyes and mouth.