A horror in the halls of Downton Abbey

This story consists of 5 parts. It is set in season 5 after the wedding of Lady Rose and Atticus aldridge. Thomas Barrow can't get his mind of Andy and hopes he will see him once again. When he is sent to the market to pick up some groceries for Mrs. Patmore he senses something strange. The sky has suddenly gone grey and then a familiar face turns up. What does fate have in mind for Downton?