Doctors perform an operation to increase brain power, hoping to find an answer to the world's problems, but the patient is still not intelligent enough to solve them. The doctors are disappointed, and allow the patient, a monkey, to regain his natural intelligence.
Martians come to Earth to discover if humans represent a threat to them. They question a human using a machine to verify his answers, and find that he is totally free of greed, hatred or deceit. The Martians leave satisfied, unaware that they questioned a mental patient.
Henry Pym invents a shrinking serum, but is trapped in an ant hill when he tests it. He is attacked by several ants, but one of them helps him escape and restore his ordinary size. He destroys the serum because it is too dangerous.
A scientist's assistant is determined to find if his time machine that sends objects into the past or future. He steals some gold ingots from the office and steps into the ray, knowing that he can never return to the present. When his journey ends, Earth is so primitive that he is cut off from all humanity, and he realizes that he still doesn't know whether the machine sends things into the past or future since it could be either the dawn or the end of time.