When Sandra and David heard their daughter Kristina had been killed by a drunk driver, they were overcome with grief. As the months went by it didn't get any easier, but one day, Sandra found a bucket list that Kristina had created. "Go to Niagara Falls." "Save a life." "Run through a field of poppies." And so these grieving parents have started crossing off the items on their daughter's bucket list—and so have dozens of strangers around the world, all moved by her joy for life that lives on.