Synopsis: Dr. Don Blake watches TV and learns that a fifth leading American scientist has publicly defected to the U.S.S.R. He is suspicious and decides to take a trip to investigate. He travels to Washington D.C. to the office of Colonel Edward Harrison, U.S. Army Intelligence. His idea is to pose as a scientist that discovered a new biological weapon and then hope the Reds come calling so he can learn what is going on. The Colonel comes along with the plan.
Blake sets up the lab and eventually attracts the attention of a Red agent. The agent poses as a news photographer and uses a gas to hypnotize Blake. He is told to leave a farewell note then is whisked away overseas. He is placed into a cell with the other missing scientists and comes to his senses.
The scientists let him know where he's at and Blake learns that they have not shared national secrets yet but are also concerned how much longer they can stand the torture. The guards come in and separate them into solitary cells. Blake uses this as an opportunity to transform into Thor. He then breaks out of his cell and confronts the guards. However the guards threaten to kill the scientists if he doesn't lay down his hammer.
He does and then is put in special locks designed for his strength. Separated from the hammer he reverts back to Blake but luckily no one sees it happen. Being smaller, he slips out of the chains and grabs the hammer (which no one could budge). Thor frees the scientists and heads back to battle the Reds. He brings down the fortress and reverts to Blake to blend in with the scientists. They all sneak out of the country and get back to the U.S.