You're on a winter dayhike when an unexpected blizzard develops. Visibility drops to nil, and you're forced to spend a night out in frigid temps. By morning, the storm has passed, but the stabbing pain in your feet has given way to stony numbness.
Hike out to medical help immediately. If you suffer from frostbite–the formation of ice crystals between your skin cells–only one treatment will do: rapid thawing in a warm-water bath, administered by professionals. Don't attempt to thaw tissues yourself: Rubbing skin causes more cell damage, and exposing numb feet to a campfire can lead to serious burns. Until you reach help, it's actually crucial that your feet stay frozen. Once rewarmed, frostbitten areas become so painful and swollen that walking is impossible–and if thawed areas re-freeze, tissue death and amputation are all but certain. To keep feet from thawing as you walk out, adjust your layers so your body feels slightly cool. (Don't dress down so much that you risk hypothermia, of course.) Quickly improvise crutches if hiking is difficult. If you cannot keep feet completely frozen, remove socks or boot insoles to accomodate the swelling and continue walking out.