Unconscious after his
bachelor party, Peter DeHaven (Jeffrey Lynn) is transported by his friends to the college dissecting room as a
practical joke. Professor Shotesbury (Edward Everett Horton) mistakenly injects him with a serum that makes him
invisible. While invisible, DeHaven learns that his fiancée, Christine (Marguerite Chapman), is only marrying him for his money. He also falls in love with Shotesbury's daughter, Joan (Jane Wyman). Meanwhile, Shotesbury is committed to a
sanatorium by his colleagues for his claims about invisible monkeys and men. DeHaven and Joan, by this time also invisible, go to release Shotesbury from the mental hospital, which they achieve by making him invisible as well. All the while time is running out for DeHaven to receive an
antidote. In the end, all receive the antidote, and DeHaven ends up with Joan. However, Shotesbury's servant Willie suddenly becomes invisible upon sitting down in the witness chair. ==Cast==