Gene Evans as Steve Karnes
André Morell as Prof. James Bickford
John Turner as John
Leigh Madison as Jean Trevethan
Jack MacGowran as Dr. Sampson, the Paleontologist
Maurice Kaufmann as Mini Submarine Officer
Henri Vidon as Thomas Trevethan
Leonard Sachs as Scientist
The Giant Behemoth (aka Behemoth, the Sea Monster and The Behemoth) is a 1959 American-British science fiction giant monster film co-production. Originally a story about an amorphous blob of radiation, the script was changed at the distributor's insistence to a pastiche of The Beast from 20,000 Fathoms (1953), though elements of the original concept remain in the early parts of the film and in the "nuclear-breathing" power of the titular monster.
The script was written by blacklisted author Daniel James under the name "Daniel Hyatt," with Eugène Lourié co-writing as well as directing. Released in the United States as The Giant Behemoth, the film starred Gene Evans and André Morell. It was distributed by Allied Artists Pictures.
American scientist Steve Karnes (Gene Evans) delivers a speech to a British scientific society, headed by Professor James Bickford (André Morell), about the dangers to marine life posed by nuclear testing. Before Karnes can return to the U.S., a real-life example of his concern materializes when Tom Trevethan (Henri Vidon), an old fisherman, receives a lethal doze of radiation; his dying word is "behemoth". Later thousands of dead fish are washed ashore.
Karnes and Bickford investigate the beach where the old man died, collecting samples which prove that radiation was the cause. Karnes begins to suspect that the "behemoth" that the old man described is some kind of large marine mammal that has been infected with radiation.
A man, his son, and their dog are the next victims of the creature. A photo of the area reveals a huge foot-print of some prehistoric animal. Dr. Sampson (Jack MacGowran), a paleontologist, identifies the creature as a 'Paleosaurus', an aquatic dinosaur that emits an electric pulse, like an eel. Karnes believes that the dinosaur is saturated by radiation, which is transmitted by the electric pulse, resulting in the burns that killed the fishermen and other victims. The radiation is also slowly killing the dinosaur. According to Dr. Samson, the dying creature will leave the ocean deeps to head up stream, seeking out the shallow waters where it was born; unfortunately death by radiation may not come soon enough to prevent the creature from wreaking havoc on London along the way.
Karnes and Bickford try to persuade authorities to close the Thames, but the military believes their radar tracking systems will be enough to detect the behemoth and prevent it from getting near the city. Unfortunately, the dinosaur appears to be invisible to radar. Dr. Sampson and some other scientists spot it from a Royal Navy helicopter, but the radar equipment tracking the helicopter sees no sign of the beast, which destroys the helicopter with its radioactive emanations. Soon, the Behemoth surfaces in The Thames and destroys The Woolwich Ferry by capsizing it.
Rising from the Thames River, the creature attacks the city, flattens several cars, and knocks a building over onto fleeing citizens. Bickford and Karnes advise the military on how to destroy the beast: bombs are out of the question, because blowing the creature to pieces would just spread the lethal radiation farther, resulting in more deaths. The two scientists propose finding a way to administer a dose of radium to the behemoth, hoping to accelerate the radiation sickness that is already slowly killing it. While they prepare the dose (which takes time because radium must be handled carefully), the behemoth continues its rampage, destroying electric towers and eventually plummeting through London Bridge back into the Thames.
Karnes and Bickford set their plan into action. A mini-sub with Karnes carries a torpedo filled with radium into the Thames in pursuit of the monster. During an initial pass, the Behemoth takes a bite out of the mini-sub, but Karnes convinces the submarine captain to have another go. This time the sub fires the torpedo into the monster's mouth.
The Behemoth roars in pain as the radium accelerates the high radiation levels that were already bringing about its death. Observers in helicopters see steam rising from the ocean, indicating the monster's demise. As Karnes and Bickford climb into a car to leave the area, they hear a radio report of dead fish washing up on the eastern shores of the United States.
The live-action scenes for The Giant Behemoth were filmed in Great Britain, including London. The model-animation special effects were shot in a Los Angeles studio, where they were also optically integrated with live-action footage. Due to budget restraints, the scene of the monster smashing a model car was used three times in the film.
Aware of the availability of master effects technician Willis O'Brien, director Lourié suggested the producers allow the King Kong creator to do the effects. Instead the work was contracted to Jack Rabin—who then sub-contracted the animation work back to O'Brien for a low flat-rate of $5,000. O'Brien's assistant Pete Peterson did most of the animation on this film, which is remarkably fluid, considering that he suffered from multiple sclerosis at the time.
Except for short bits in the climax of It's a Mad, Mad, Mad, Mad World, this film marked the last time that Willis O'Brien designs and animation would be seen by the public.
In an odd connection between Willis O'Brien and his most famous creation, stock screams that were used in King Kong can be heard in the scenes where the creature attacks the ferry and when it invades London.
In Video Movie Guide 2002, mention of the stop-action animation was made but with the proviso that "the film monster wasn't bad but (Willis O'Brien) was clearly working with a low budget.: Film reviewer Andrew Wickliffe considered the preamble to the appearance of The Giant Behemoth was more interesting than the rampage that followed. He saw the film as "too British" and not much fun. On the later release of the film in a package with other sci-fi features, film reviewer Glenn Erickson made an interesting observation that The Giant Behemoth was derivative, speculating "... director Eugène Lourié apparently instructed writers Robert Abel and Alan Adler to repackage his original The Beast from 20,000 Fathoms, copying whole scenes and situations. The structure and script are almost a verbatim clone, right down to the dotty paleontologist ..."