Three top secret, experimental vials stored at subzero temperatures were flown into Liberia last week in a last-ditch effort to save two American missionary workers who had contracted Ebola, according to a source familiar with details of the treatment. A representative from the National Institutes of Health contacted Samaritan's Purse in Liberia and offered the experimental treatment, known as ZMapp, for the two patients, according to the source. The drug was developed by the biotech firm Mapp Biopharmaceutical Inc. The patients were told that this treatment had never been tried before in a human being but had shown promise in...