The Giant Behemoth is a 1959 British-American science fiction monster film directed by Eugene Lourie. The film stars Gene Evans, Andre Morell, and John Turner.
The film follows a team of scientists who are studying the effects of atomic bomb tests on the ocean's ecosystem off the coast of Ireland. They discover that the tests have caused dangerous blobs of radiation to form in the ocean, which are causing mutations in the local marine life.
As they investigate further, they discover that the radiation has awakened a dormant dinosaur, known as a Behemoth, which had been living deep within the ocean for millions of years. The Behemoth emerges from the ocean and begins to wreak havoc on London, causing destruction and chaos in its wake.
The team of scientists, led by Steve Karnes (Gene Evans), must find a way to stop the giant behemoth before it destroys the entire city. They come up with a plan to use a special radioactive isotope to attract the behemoth back into the ocean, but they must race against time before it's too late.
In the end, the plan is successful, and the behemoth is lured back into the sea, where it dies from its exposure to the radioactive isotope. The film ends with the scientists warning of the dangers of atomic bomb tests and the potential for unforeseen consequences.