Lang replaced John Bates as Lord Grantham's valet when Mr. Bates was blackmailed by his estranged wife, Vera, to return with her to London. Suffering from shell shock, he was later dismissed as his condition did not allow him to continue employment at this stage. Sarah O'Brien forms a bond with Lang after she admires his skills as a valet, which he tells her learns from his mother, a lady's maid like O'Brien, something which she approves of. O'Brien also reveals to Lang that her favorite brother, who later died after returning to the Western Front, was suffering from shell shock as well. He also slightly bonds with Ethel Parks when she sees him sewing. Ethel is amazed at his talent and stares in awe. He did unintentionally hurt Mrs. Patmore when he talked about her nephew Archie being shot for cowardice.
- 在早期新闻材料中，该角色被命名为安德鲁·朗（Andrew Lang）