He did not return. His firm hires a private detective, but even they cannot find him. Edith's worries only worsen. Cora is certain they would have heard if something terrible had happened.

Why was Michael Gregson killed?

Gregson went to Germany to establish citizenship so that he could get a divorce and then marry Lady Edith, but before he could do that he was killed by a gang of Nazi thugs in Munich.

Does Edith get marigold back?

Edith repeatedly visited Yew Tree Farm to see her daughter, arousing the suspicions of Drewe's wife. ... Edith reclaims her daughter and leaves in the hope that she can begin a new life and finally find happiness with Marigold. Back at Downton, Cora learns from Mrs Drewe that she has a third grandchild.