Lovely scenery but you know if you get Edmund Gwenn, you're going to get whimsy and lots of it. (He did, after all, play Kris Kringle in the original "Miracle on 34th Street".) John Forsythe basically got lost among the rest of the cast who were all stronger and that includes "The Beaver" himself, Jerry Mathers.
As at least someone else mentioned, it did remind me very much of "Arsenic and Old Lace" which had a stronger story and, in the film, Cary Grant. It's interesting that, at one point, Edmund mentioned that he might have elderberry wine before he was went over to Mildred N's and this was the drink that was used for poisoning in the other story.
I found it contrived but fairly entertaining and mildly funny. Worth a view but don't go out of your way.
7 out of 10.