WOBURN — A prison guard, an inmate and the inmate's mother face charges in connection with a scheme to bring drugs into the Souza-Baranowski maximum security prison in Shirley.The Middlesex district attorney's office says 30-year-old guard Brandon Beach was held Monday on $50,000 bail after pleading not guilty to charges including heroin and cocaine trafficking.Sixty-nine-year-old Sandra Lomastro of Fall River was released on personal recognizance on a charge of conspiracy to violate drug laws.