I could hear the scream from across the room.  It was shrill and filled with panic.  Any parent can identify the difference between the cries of normal toddler discomforts and a true emergency.

I dropped what I was doing in the kitchen and found my three-year-old lying motionless on the ground, unable to move his left arm. My five-year-old was looking sheepishly down at the carpet, afraid to meet my gaze.