"The Unknown" (1946) was the final, and the weakest entry in Columbia’s I Love A Mystery series. The screenplay is attributed to four persons; Malcolm Stuart Boylan, Julian Harmon, Charles O’Neal and Dwight Babcock (the latter two supplying the adaptation). It too was directed by Henry Levin.
Heavy on atmosphere, and tortuous of plot, the film begins with a long prologue with a voiceover. In the Martin Plantation in Kentucky, deep in a South steeped in myth and conservatism, lived Captain Martin, his domineering wife Phoebe, and their three children, Ralph, Edward and Rachel. Despite her parents plans for her to wed another, Rachel has secretly married Stanley Arnold six months before, just before he had been called abroad. On the very night of Rachel’s unwanted engagement party, Arnold returns to claim his wife. Rachel’s father, Captain Martin flies into a terrible rage, and pulls a gun on Arnold. In the subsequent struggle, Captain Martin is shot dead. Mrs. Phoebe Martin, who rules the family with an iron hand, orders a weeping Rachel to her room, and pulls a gun on Arnold, and order him out of the house the way he came in, via the secret tunnel to the family vaults. The remaining family, along with some of the servants, inter the body of the dead Captain Martin in the walls of the fireplace, and brick it up. They also wall themselves inside the confines of the Martin house, Mrs. Martin determined that they will all stay inside the walls of the house until she dies…this is all told in Mrs. Martin’s voice, in the voiceover, a voiceover she states she is making from the grave...
The scene cuts to many years later. A taxi stops in front of the main gates of the Martin homestead, a black wreathe hanging on the wrought iron bars. From out of the taxis alight Jack Packard and Doc Long, in the company of a beautiful young woman. She is Miss Nina Martin Arnold, and with the announced death of her grandmother, she is here for the reading of the will. Jack and Doc have been hired by a Mr. Franklin to bring her here, and to look after her interests. Mr. Franklin is Nina’s ward, a wealthy man who has paid for Nina’s upbringing and schooling, although she has never met him…
As they walk with their suitcases, they catch sight of a curious building off to one side, which Jack states must be the family mausoleum. Watching them from outside is mysterious woman, wearing a diaphanous and flowing dress. Noting their interest in her, the mysterious girl runs off into the bushes. Shrugging, they march up to the front door of the mansion. After knocking on the door (a black wreathe hanging here too), and are led inside by the black butler, Joshua.
The house is huge, gloomy, and somewhat creepy. The rooms are huge, and much of the furniture in them shrouded in sheets to protect them from dust. Inside the drawing room, Joshua introduces them to the family attorney, Mr. Cawthorne, and leaves.
Cawthorne is somewhat surprised to meet Nina. He never heard mention that the late Mrs. Phoebe Martin had a granddaughter, nor that Rachel Martin had a daughter. Moreover, he tells them he is surprised to learn they know that one of the stipulations of the will was that those benefiting had to spend the night in the house. When Jack tells them that Nina’s ward, the mysterious Mr. Franklin, told them about the will, Cawthorne states he’s never heard of a Mr. Franklin. He’s also somewhat bemused and puzzled by Nina’s mysterious and unknown benefactor who only in his last letter revealed to Nina her true identity, and the fact that her mother was still alive!
I’ll stop here, and not give away any more of the story. While there are a few interesting atmospheric elements, such as a baby crying where there isn’t any baby (hmm…where did we hear that before?), cantankerous uncles, psychotic daughters, secret tunnels, murder and vanishing wills, this is a grade C "I Love A Mystery" story at best.
Bannon had this to say about the final film in the I Love A Mystery series:
"The Unknown" had a pretty fair cast, mostly Columbia’s contract players, but the story was a little on the tired side. Jeff Donnell and Nina Foch, who is without question the most talented of the girls on the contract list, did the female leads, and a boy named Bob Scott was the leading man. He has been on the lot only a few months and I hadn’t done much more than say "Hello" to him until this picture.
Both Bart Yarborough and I have the feeling this may be the swan song for the Mystery series. The writing is so bad that is almost seems they’re content to let it die. It’s very sad because it had excellent potential if it had been done right. Instead of continuing with the Carlton Morse stories they have just turned the studio’s staff writers loose on the scripts and what they’ve turned out couldn’t even them a passing grade in a high school play-writing class. If it is cancelled that will be the end of Bart at Columbia. Since I’m on contract I’ll just get shoved onto other things.
Jim Bannon was unfortunately correct. It wasn’t until years later that another, alas ill-fated, "I Love A Mystery" production was initiated, the 1969 Television Pilot.