Just what was it that convinced shock film producers that the leaden, shambling gait of a sonambulant monster would inspire untenable terror in their audience? Through several sequels, the Mummy pursued a squealing Evelyn Ankers at a snail's pace, aided in his pursuit by the heroine's unerring knack for finding sticks and stones and myriad ground clutter to stumble over. The rag-wrapped pursuer always managed to snare his prey.

Likewise, the zombie shared the Mummy's obvious motor impediments. The zombie's capacity to induce fright was limited to the relentlessness of his pursuit -- wide-eyed, mouth agape, staggering into a hail of bullets, he just kept coming.

With the added twist of alien-powered zombies, Invisible Invaders parlayed the notion Ed Wood had showcased to inadvertent comic effect in Plan 9 From Outer Space. From their Moon-based bastion, Earth's would-be conquerors set about re-animating the recently deceased, conscripting a makeshift army of shuffling cadavers to do their dirty work. The first to be resuscitated is crack nuclear researcher John Carradine, a scientist so skilled he manages to blow himself up in the film's opening moments. His corpse inhabited by an invisible alien emissary, Carradine visits his scientist pal Philip Tonge, explaining the ramifications of the alien agenda.

Earthlings refuse to cave in to the outrageous demands for surrender and the aliens are forced to issue a final, public ultimatum. And what forum do they choose from which to address the cowering populace of Earth? -- the announcing booth at a hockey game. Just why the aliens think that anyone of significant world influence will be attending the game is unclear. Just the same, a baggy-eyed zombie staggers into the booth, chokes the announcer and commandeers the microphone.

Soon after, stock footage natural disasters sweep the planet. Cities are evacuated and a dark-eyed army of the living dead soon roam the land. Weasely nuke doctor Robert Hutton and his glamorous Gal Friday Jean Byron are pressed into service and find themselves sharing a zombie-proof bunker with buzz-cut army honcho John Agar. As a by-product of Hutton's cowardly conniving, this fractious band of researchers tumbles to the fact that high-frequency sound can stop a waddling zombie dead in his tracks (so to speak). Fashioning an armory of high-pitch packing rifles, earthfolk rise to the challenge and vanquish their cadaverous conquerors.

A charitable critic would point out that director Edward L. Cahn was severely hampered by this film's microscopic budget. The disaster footage is obviously from stock, an auto wreck was actually Robert Mitchum's fiery death scene from Thunder Road (and later turned up in They Saved Hitler's Brain) and sets are put to repeated use to comical effect. For the most part, the zombies are portly, middle-aged men in business suits with a dab of charcoal under each eye. This is true terror?

It's been pointed out that this modest shocker was an arguable influence on George Romero's horrific breakthrough Night of the Living Dead. The similarities are inescapable -- witless, droopy-eyed zombies, grainily stark black and white photography, and an addled band of survivalists defending their besieged sanctum, squabbling among themselves as the zombies pound relentlessly at their fortress door. Many of the same elements were seen to marginally horrific effect in The Last Man on Earth, a European production starring Vincent Price and based on Richard Matheson's I Am Legend (lensed again some years later as The Omega Man with Charleton Heston).

Director Cahn seems barely able to prevent his hyper cast from chewing the script to bits, with the hamming of Hutton and Agar particularly noteworthy. Philip Tonge on the other hand seems stubborny disaffected while John Carradine is -- John Carradine.

The sonic solution is certainly nothing new to sci fi. The truculent invaders of Earth vs. The Flying Saucers were dispatched with sound waves as were the boxy robots of Target Earth. The more recent Mars Attacks featured a not dissimilar hi-fi finale. But why was sound the screenwriters's default as an alien Achilles' heel? Why not blinding beams of light? Or an olfactory assault? Surely we've enough odious industrial pollution to repel several alien squadrons. Or taste? Why not spike their alien rations with generous dollops of Chinese mustard?

But B film drive-in fare was never long on originality. In the case of Ed Cahn's output, an enjoyably grizzly premise and suitably snappy pacing was usually enough. Sadly, Invisible Invaders shambles through its horrific paces with the tortoise-like gait of its protagonists.

The Last Man on Earth (1964)
The always elegant Vincent Price brings grim poignancy to his portrayal of the sole survivor of a vampiric plague that's turned the rest of the human race into a legion of the walking dead. Each night they assault his barricaded home, and each day he sets about driving stakes through their sleeping hearts.

Acting: B-
Atmosphere: C+
Fun: B+

Zombies of Mora Tau (1957)
Director Ed Cahn, who later lensed Invisible Invaders, helmed this saga of sunken sea-zombies jealously guarding a cache of stolen gems. When their coveted booty is threatened with thievery, they awake and wade to the rescue.

Acting: A+
Atmosphere: A-
Fun: A

I Eat Your Skin aka Voodoo Blood Bath aka Zombie (1964)
Director Del Tenney's final film survived several incarnations and multiple titles before emerging at last as I Eat Your Skin. It's the tepid tale of a playboy/author/investigator and a cloistered horde of unintimidating Caribbean zombies.

Acting: C-
Atmosphere: C
Fun: C+

Revolt of the Zombies (1936)
A sequel in name only, the Halperin brothers produced this ill-conceived follow-up to their classic White Zombie. A very young Dean Jagger stars as the heir to a jungle-bound Cambodian plantation where bizarre rituals are enacted in an attempt to assemble an army of the living dead.

Acting: C-
Atmosphere: D
Fun: D+