
Terror sweeps Los Angeles at night as scientists chase a surge in magnetism and radioactivity. They find a man‑made isotope that siphons energy from nearby mass, doubling its size every few hours. Though microscopic now, it will soon grow large enough to endanger Earth, with no solution. The Deltatron footage is reused from the 1934 sci‑fi film GOLD.
Does The Magnetic Monster have end credit scenes?
No!
The Magnetic Monster does not have end credit scenes. You can leave when the credits roll.
Explore the complete cast of The Magnetic Monster, including both lead and supporting actors. Learn who plays each character, discover their past roles and achievements, and find out what makes this ensemble cast stand out in the world of film and television.

Strother Martin
Co-Pilot

King Donovan
Dr. Dan Forbes

Richard Carlson
Dr. Jeffrey Stewart

Harry Ellerbe
Dr. Allard

Roy Engel
Gen. Behan

Kathleen Freeman
Nelly

Leo Britt
Dr. Benton

Michael Fox
Dr. Serny

Byron Foulger
Mr. Simon

Curt Siodmak

Lee Phelps
City Engineer

Jean Byron
Connie Stewart

Juney Ellis
Spinster

William Benedict
Albert

Leonard Mudie
Howard Denker

Frank Gerstle
Col. Willis

John Vosper
Capt. Dyer

John Zaremba
Chief Watson

Michael Granger
Kenneth Smith

John Dodsworth
Dr. Carthwright

Jarma Lewis
Stewardess

Douglas Evans
Pilot

Watson Downs
Mayor

Elizabeth Root
Joy
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Challenge your knowledge of The Magnetic Monster with this fun and interactive movie quiz. Test yourself on key plot points, iconic characters, hidden details, and memorable moments to see how well you really know the film.
Who plays the lead investigator Dr. Jeffrey Stewart?
Leonard Mudie
King Donovan
Richard Carlson
John Carradine
Show hint
Read the complete plot summary of The Magnetic Monster, including all major events, twists, and the full ending explained in detail. Explore key characters, themes, hidden meanings, and everything you need to understand the story from beginning to end.
Dr. Jeffrey Stewart [Richard Carlson] and Dr. Dan Forbes [King Donovan], a pair of investigators from the Office of Scientific Investigation (OSI), are drawn into a perplexing anomaly at a local appliance store. In a strange twist of timing, every clock in the shop halts at once, and ordinary metal items become magnetized as if drawn by an unseen force. The clues point upward to an office directly above the storefront, where a jumble of scientific equipment sits amid a dead body and signs of radioactivity. The mystery seems to have leaped beyond the room itself, reaching into the air and the surrounding environment.
As the OSI team digs deeper, they persist in seeking public input and end up on a fateful flight where a scientist, Dr. Howard Denker [Leonard Mudie], is traveling with a heavy, closely guarded briefcase. Denker is already showing signs of radiation sickness tied to whatever he carries. Before he dies, he confesses to experiments with an artificial radioactive isotope, serranium, which he had bombarded with alpha particles for an extended period—200 hours, to be exact. The revelation is chilling: what he created has somehow taken on a life of its own.
The island of danger centers on serranium’s eerie behavior. The unstable isotope must absorb energy from its surroundings every 11 hours; with each cycle it doubles in size and mass, releasing deadly radiation and an astonishing magnetic field. OSI scientists realize that, at this pace, the isotope will soon become heavy enough to influence the Earth itself, potentially altering the planet’s rotation and even breaking free from its solar orbit. The creature is resilient beyond conventional means of destruction or containment.
A theoretical solution emerges from Stewart’s calculations: the element might be overfed to force a fission into two stable elements. Yet the energy required is astronomical—nearly one gigavolt—and no ordinary device can provide such a surge. The only practical answer appears to lie with a Canadian experimental power generator, the Deltatron, housed in a cavern beneath the ocean and designed to deliver the kinds of energies serranium demands.
With intergovernmental agreement, serranium is transported to the Deltatron project site. Yet at the last moment, Dr. Benton, the engineer in charge, raises a critical objection. Facing impending catastrophe, Stewart—the lead OSI agent—takes control of the massive, cavern-filling machine. He powers it to maximum output and, in a tense race against time, manages to trigger a final surge that pushes serranium beyond its limits and annihilates it. The price is steep: the Deltatron itself is destroyed in the process, but the dangerous isotope is extinguished and the trace magnetism it produced vanishes.
In the aftermath, the Earth is saved, and life returns to normal. The film closes with Dr. Stewart [Richard Carlson] and his pregnant wife Connie [Jean Byron] celebrating a quiet, hopeful future as they purchase their first home and prepare to start a new chapter together, reinforcing the human stakes behind a victory that kept the world safe from a miniature apocalypse.
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