Boris Karloff once again gives a performance that outclasses a shoddy production. The last of the four Mexican-American cheesy B's that the genre star made before his death, it stars Karloff as John Mayer, a scientist in 19th century Europe. He's perfected a ray machine; it attracts the attention of a rather harmless looking spaceman. Believing that Mayers' invention must be destroyed, the spaceman (Sergio Kleiner) forces lady killer Thomas (the hulking Yerye Beirute) to work for him, and the psycho infiltrates the Mayer household.
Also starring Enrique Guzman as young scientist Paul Rosten, Christa Linder as Mayers' lovely niece Laura, and an appealing Maura Monti as Mayers' disfigured assistant Isabel, "The Incredible Invasion" a.k.a. "Alien Terror" may be just the thing for some lovers of cinematic trash. Granted, it can be slow and dull at times, with uninspired direction and a silly script co-written by actor Karl Schanzer (whom you may remember as the sleazy lawyer in "Spider Baby"). It doesn't have any real atmosphere, and the score is hilariously ineffective. But it does offer some fun, provided you're partial to this sort of thing to begin with.
As with the other movies, this had Mexico-lensed scenes helmed by Juan Ibanez, and Jack Hill (the B movie great who gave us classics like "Coffy", "The Big Doll House", and "Switchblade Sisters") handling the L.A. studio scenes. (Jose Luis Gonzalez de Leon is credited as a co-director.) Sadly, Karloff's failing health is apparent; he couldn't move about very much, and required the use of a mobile oxygen unit, but he's still effortlessly delightful, giving as much as he can to a fairly standard kind of genre character.
It may be of some interest to people to compare these four movies and decide how best to rank them. This isn't the most entertaining, but neither is it the worst of the bunch.
Five out of 10.