Dementors Attack the Hogwarts Express   It is a little known aspect of the Second Great Wizarding War that the Order of the Phoenix occasionally used the Hogwarts Express as a means of secret communication.  When required,  a brave squib engineer - Cornelius Melchett - would take the locomotive, unencumbered by rolling stock, at high-speed to points all over the country conveying secret messages and items of great importance.  Since he was a squib, he was not closely monitored by the M