Invisible Agent was made seven months after the bombing of Pearl Habor and the American entry into World War II. Thus the invisible man capers of the previous films have now been rewritten with a patriotic bent. Following a montage of scenes depicting the outbreak of war, The Invisible Man immediately offers his assistance to the State Department. The villains of the show are the ever-dependable Nazis and the Japanese with Peter Lorre outfitted in round glasses like a cartoon caricature of the Japanese from the era. (Lorre, who was in actuality an expatriate German actor, gives a performance that manages to steal much of the film).
Invisible Agent is a marked improvement over the previous entry The Invisible Woman, which was almost completely played for laughs and is the series low point. Not that that the comedy element doesnt feature here. There are wacky images such as Jon Hall taking the serum on the plane and stripping his clothes off while parachuting down and observers on the ground seeing an empty parachute land. There is also an eminently silly scene at Ilona Masseys house as J. Edward Brombergs pompous Nazi official arrives with dinner, which involves the invisible Hall making fun of Bromberg, spilling food on him, taking his chicken leg and finally tipping the table over him.
On the other hand, these sit alongside some imaginative and well-staged scenes. Like where Sir Cedric Hardwickes Nazi official sets a trap and lures Jon Hall to his office and keeps him there at gunpoint, insisting he sway in the chair so he can be sure where he is, before Hall sets a wastepaper basket on fire and soon has the whole room alight where he causes merry chaos as the soldiers outside rush in to capture him, before escaping out the window and down the ladder the fire department bring up the outside of the building. There is another great scene where Hall sneaks into J. Edward Brombergs cell and torments him, before knocking two guards out and making an escape dressed in an SS officers uniform with the collar turned up and cap pulled down, followed by a great extended climax getting away on a plane, dropping bombs on the Nazi invasion airfield and finally being forced to jump out of the plane after it is shot down over England.
Director Edwin L. Marin was a steady director of Westerns and comedies throughout the 1930s and 40s. His only other venture into genre material with the Reginald Owen starring version of A Christmas Carol (1938).
Screenwriter Curtis (or usually Curt) Siodmak was a German native who had worked as a novelist and began writing scripts in Germany with the science-fiction film F.P.1 Does Not Answer (1932), before fleeing to the US with the rise of the Nazis. His genre scripts include Trans-Atlantic Tunnel (1935), The Ape (1940), Black Friday (1940), The Invisible Man Returns (1940), The Invisible Woman (1940), The Wolf Man (1941), Frankenstein Meets the Wolf Man (1943), I Walked with a Zombie (1943), Son of Dracula (1943), The Climax (1944), House of Frankenstein (1944), The Beast with Five Fingers (1946), Tarzans Magic Fountain (1949), Riders to the Stars (1954), Creature with the Atom Brain (1955) and Earth Vs the Flying Saucers (1956). He also directed/wrote several films with Bride of the Gorilla (1951), The Magnetic Monster (1953), Curucu, Beast of the Amazon (1956) and Love Slaves of the Amazon (1957). Siodmak also wrote the classic novel Donovans Brain (1942) about a millionaires disembodied brain that ends up mentally controlling the scientist that removed it, which has been thrice filmed as The Lady and the Monster (1944), Donovans Brain (1953) and Vengeance/The Brain (1962). Siodmaks lesser known follow-up Hausers Memory (1968) about transplanted memories was also filmed as the tv movie Hausers Memory (1970).