1968's "Incredible Invasion" (Invasion Siniestra or Sinister Invasion) completed the Boris Karloff quartet of Mexican titles for producer Luis Enrique Vergara, as shown by the absence of Julissa as his daughter, replaced by German beauty Christa Linder, Yerye Beirute from "Fear Chamber" cast as the serial killer Thomas. Prof. John Mayer offers the octogenarian actor his greatest screen time at 24 minutes, a forward looking scientist of 1890 whose new invention produces a laser that destroys a boulder (a nice nod to "The Invisible Ray" of 1936), but alarmingly earns the attention of a space invader out to put an end to mankind's interference. Why the alien decides to use an accomplished razor wielding psychotic as a go between, continuing to supply him with more female victims to butcher, makes this a truly unpleasant viewing experience, and once Mayer too falls under the telepathic control of its evil influence (both characters giving off deadly signs of radiation) the picture simply stops dead with no further development. The local villagers are in an uproar as they search for the missing victims, every woman save for Mayer's daughter just another corpse for the morgue, far too much footage given over to sleazy exploits than its ailing star. What could have been the best of this final four is a jumbled collection of ideas that fail to coalesce, though Boris as usual is able to make a silk purse out of a sow's ear in beefing up Mayer's resistance to his brain's unwelcome occupant. The lone alien on display looks like a reject for Gerrit Graham's part of Beef in Brian De Palma's "Phantom of the Paradise," essentially a parody before there was such a thing. It's an astonishing twist of fate that this Karloff feature would actually echo the nuclear message of Lugosi's farewell "Plan 9 from Outer Space," whose invaders were just as rash and incompetent, while the mob of torch wielding villagers offer a pleasant reminder of the good old days at Universal. Few people could have caught up with this obscurity until the butchered VHS version called "Alien Terror," not the best way to enjoy Karloff's last screen performance, though sadly ironic is the ultimate fate of writer/producer Luis Enrique Vergara, following his leading man into the afterlife by dying just one year later at a shockingly youthful 47.