Show of the week: Masterpiece: Downton Abbey, Season 3

It’s 1920 and all is aflutter at Downton Abbey. Not only will Lady Mary finally wed Matthew Crawley, but her grandmother (Shirley MacLaine) is about to arrive from the U.S. with ideas about tradition that unsettle the dowager countess (the inimitable Maggie Smith). Add to that Lord Grantham’s sudden money problems and an unexpected inheritance for Matthew, and it’s no wonder the upstairs aristocrats are sniping, all while the downstairs staff copes with separate dramas. Though the busy story gets choppy, it’s still nice welcoming back old friends. Sunday, Jan. 6, at 9 p.m., PBS