"Students,” Principal Benson said, “Although I want to first assure you that you will be safe and secure, it appears that we have an emergency on our hands.”

A tanker train has derailed on the East side of Missoula, Montana and two chlorine gas tankers are in danger of puncture. As Mr. Benson begins to describe the evacuation plan, Ami Gibb cannot accept her unrelenting misfortune. Having lost her father in a car accident four months earlier, she needed no more bad news. But the bedlam of an evacuation isn’t the bad news for Ami. The bad news is that her ten year old sister sits across town, alone and within a mile of the derailment. With their mother on vacation in Toronto, it’s up to Ami to save her sister.

When the Light Goes Out is the story of Ami’s crosstown journey to rescue her sister. What she finds is that the greatest danger doesn’t always lie within the natural disaster; it lies within the chaos of the unknown.