If you took the underlying premise of Invasion of the Body Snatchers ('56) and mixed in a bit of Angry Red Planet ('60), you would have The Day Mars Invaded Earth (DMIE). Black and white films were becoming less common by '63, so it was clearly second-bill drive in material. This low-budget production has its weak points, but maintains a moderate level of quality, a certain film-noir flavor and tension. It tells the tale of martian energy-intelligences replacing key people on a Mars probe program.
Quick Plot Synopsis
A NASA probe to Mars lands and. Its rover explores for a few minutes before being burned up by an energy surge. Dr. Dave Fielding feels oddly empty for a moment, but goes out to face a crowd of reporters. When he leaves, his double is seated at his desk. Dave flies home to California to be with his family who are staying in the guest house of a mansion belonging to his wife's family. The kids, 10 year-old Rocky and teen Judy are happy to see him, but his marriage to Claire is in deep trouble. Tensions between Dave and Claire make it less obvious, at first, that they are seeing their doubles walking around the estate. Eventually, things get obviously creepy and the family pulls together. They are unable to leave the estate, due to a stuck main gate. Dave encounters his double in the "Big House". Double-Dave tells him how martians are energy-like intelligence beings without bodies. They traveled to earth via the probe's radio transmitter. (that's what fried it) On earth, they plan to replace key people to squash any further earth missions to Mars. Since Dave's wife and kids would recognize a duplicate, they had to be replaced too. Family friend, Web, gets the gate open, but on his way back, Mars-Dave uses his energy-ness to burn Web into ash. The family all get in the car and leave with Mars-Web driving. The camera pans down into the empty swimming pool to reveal five body shapes of ash. The pool's jets turn on, washing the ash outlines away. The End.
Why is this movie fun?
The alien-takeover trope is usually fun. The empty mansion and estate make for an interesting closed environment for the drama. The unresolved ending, in which the duplicates all drive away happily on their way to subtle sabotage, is interesting. In DMIE, the pods win and probably still among us.
Cold War Angle
This is more allegorical than overt. The traditional fear of nefarious "others", the not knowing who you can trust, the sinister plot behind it all, these are solid Cold War angst themes.
Venerable Sub-Genre -- The alien-takeover sub-genre is one of the key features of 50s (and 60s) Cold War angst movies. The earliest include The Man From Planet X ('50) and It Came From Outer Space ('53). The most famous of the genre is Invasion of the Body Snatchers ('56). Films of this genre were becoming less common by the mid-60s, but it wasn't played out yet. DMIE is one of the lesser-known members of the set.
Angry Invisible Mars -- The red planet often got a hostile tone in literature and movies. H.G. Wells' famous 1898 novel described them as "intellects vast and cool and unsympathetic," who "drew their plans against us." In Angry Red Planet ('60) the martians expel the earthlings with a warning to never come back. We're too immature of a species. (e.g. war, greed, etc.) DMIE has a similar subtext as Mars-Dave tells Earth-Dave that they came to stop any future Mars missions from earth. They "invaded", not to take our home (as was often the case), but to preserve their own from us.
Blame the Aliens -- Several movies seek to place the blame on aliens for American space program failures. (of which there were many). War of the Satellites ('58), Cape Canaveral Monsters ('60), Planets Against Us ('62), etc., quietly admitted that NASA was not off to a good start. Rather than doubt our own genius, it was more fun to imagine alien sabotage.
Inexpensive Fancy Sets -- Most of the action in DMIE is set in and around the Greystone mansion in Beverly Hills. It was constructed in the late 1920s for the son of an oil tycoon, Edward Doheny Jr. His wife, Lucy, sold the estate in 1955 to a man who rented it for movie location shooting. The property later became a park and more movies were shot there. Some titles include The Invisible Boy ('57) and Picture Mommy Dead ('66). The orderly and tidy gardens of the estate make for an interesting contrast to the confusion the characters face.
Natural Noir -- The invasion angst premise just naturally lends itself to the noir style. Suspicion, uncertainty, fear, they all factor in. Director Maury Dexter uses the setting of the Greystone mansion fairly well. The staid and orderly grounds are ironic backdrops for uncertainty and fear (such as when Claire is 'chased' with the footsteps sounds). When Dave explores the "big house", Dexter uses a lot of up-angle camera and uplighting, giving the otherwise comfy surroundings an unsettled look.
Bottom line? BMIE is hardly a gem, and the pace is pretty slow at first. There are virtually no special effects, creepy aliens or fancy technology, etc. to satisfy the mainstream sci-fi fan. For more devoted fans of the genre, who enjoy the alien-takeover type, the latter half gets much more interesting.