Christy Gardner, an Army vet, lost both her legs after an attack overseas. She got Moxie, a service dog, to help with daily tasks. But more importantly, during her darkest days, Gardner says her golden retriever was the only thing that stopped her from ending her own life. She's felt indebted to her dog ever since. And to pay back the debt she feels towards Moxie, she came up with the sweetest plan: to pay it forward. Steve Hartman reports.