Teen Kathie Eleanor Merrick (Elizabeth Taylor) finds a dog in the woods, takes him home and dubs him "Bill." But after Bill is injured and goes missing, the dog is shipped from hospital to military training center to Europe, where he aids the Americans during World War II. He and Kathie meet again, but Bill, hardened by the war, is quick to turn on strangers. Hoping to keep him out of trouble, Kathie gets help from volunteer lawyer Harry MacBain (Frank Morgan).