A group of scientists visit an unorthodox scientist in the South American jungle where he experiment son them to minaturise them and then tries to stop them escaping. This is an early version of the mad scoentist making people small and for 1940 is very well done. The effects were nominated for an Oscar and is reputedly the first sci-fi film made in Technicolor. The combination of colour and effects make this visually impressive for when it was made. Janice Logan is good as the female character in one of her very few films.