Life is about to change for young Sam Alden. Home for a traditional Christmas celebration, the usually robust young man worries his family with his drawn appearance and persistent coughing. Subsequent tests reveal the cause - degenerative heart disease. His condition rapidly deteriorates until his doctors determine that only a heart transplant can offer him any hope of survival. Putting aside their fears, Sam's large and loving family rallies round him. Drawing strength from each other, and from an optimistic Sam, his parents keep watch over him, awaiting decisions that could give him the chance to fulfil the promise of Thursday's Child.