While the Professor and the invisible Kitty are off visiting the lodge of the millionaire Russell, the gangster Blackie Cole (Oscar Homolka) sends in his gang of moronic thugs (including Shemp Howard) to steal the device. With the machine back at their hideout, however, they cannot get it to work. By now, Kitty has returned to visibility, and the thugs are sent in to kidnap her and Gibbs. However, she has learned that some alcohol will restore her to invisibility, and uses this to defeat the gang (with help from Russell).