Professor Gibbs (John Barrymore) believes he has made a breakthrough in his research, but he needs both funds and someone to experiment upon to be truly sure. As far as the money goes, he is relying on millionaire playboy Richard Russell (John Howard) in whose grounds he lives and has his laboratory, but that may be about to dry up as yet another young woman sues Russell for his fortune. Therefore Gibbs decides to head for the newspaper offices to alter his advert: he will now experiment on someone for no money...
If you looked at that cast list, largely made up of expert character actors and character comedians, you might consider them overqualified for such a deeply silly film, but headed by the soon to be deceased Barrymore, his glory days well behind him, all that talent worked up a surprisingly effective head of steam as far as the humour went. He certainly seemed to be enjoying himself in a fluff role light years away from his beloved Shakespeare, as by this stage his larger than life personality appeared to lend itself less to serious drama and more to sustained daftness.
As for our title character, she was a model, Kitty Carroll (Virginia Bruce - apparently a last minute replacement for a highly unlikely Margaret Sullavan) who bears her boss great umbrage for his bullying ways, and seeks to find an alternative method of employment. When she shows up at the lab, Gibbs is shocked because he expected a man, and she is shocked because he is utterly sincere about turning her invisible - well, it's either her or his housekeeper Margaret Hamilton (fresh from The Wizard of Oz), who is extremely reluctant. Which is just as well seeing as how the experiment relies on the subject being utterly nude for the duration.
That's right, they had found a way to get a naked woman into a movie without upsetting the Hays Code of censorship in 1940, even if it was to render her unseen to human eyes. One injection of serum and a go in the ray machine and the stage was set for screwball sauciness as the now starkers Kitty is delighted at her new abilities and heads straight over to the offices of her boss (Charles Lane) to freak him out by making clothes walk around on their own and slapping him about without him being able to see who is doing all this. But that would make for a somewhat limited plotline, so gangsters are introduced.
Of course they are, as emigrant hood Oskar Homolka, homesick for the Old Country, wants to use the machine to escape back there under the authorities' noses. He sends his gangsters, including Edward Brophy and one time Stooge Shemp Howard, over to Gibbs' place to steal the equipment, but when he tries it he finds all it does is alter the loud voice of Foghorn (Donald MacBride) to a high pitched squeak - he needed the serum, you see. I told you this was a silly movie, but with such luminaries as Charles Ruggles as Russell's harrassed butler doing his best to wring laughter out of ridiculous material, you cannot say there is no entertainment value. Predictably, the invisible Kitty falls for Russell, but their relationship is hampered by the fact that he cannot see her, although titillation stemming from her nudity is stronger than much material of the time. No matter how sceptical you may be at the outset, give this a chance and you could surprise yourself into chuckling.