Steve McQueen’s “Blitz” follows the epic journey of George (Elliott Heffernan), a 9-year-old boy in World War II London who is sent to safety in the English countryside by his mother, Rita (Saoirse Ronan). George, defiant and determined to return home to his mother and grandfather Gerald’s (Paul Weller) home in East London, embarks on an adventure, only to find himself in grave danger as a distraught Rita searches for her missing son.