I must have popped the Intrepid's trunk open by accident last night (or maybe the night before; I haven't driven it in two days), so that means the little light in the trunk was on all that time.
That plus below zero temperatures add up to (you guessed it) drained battery. And I mean, stone cold drained.
Luckily I have one of those battery booster things and got it started about 30 minutes ago. I'm going out now to see if the battery is actually charging.
UPDATE: Sweet. No more flickering dash lights; I think the beast will live.