If you haven't seen many serials, this would be a good start. If you're a serial veteran, you'll recognize almost all of the cliffhanger endings, which have been lifted from other Republic serials. Richard Webb, later TV's Captain Midnight, delivers a stiff performance and a lot of punches: at least one set per chapter is demolished in a slugfest. John Hamilton, TV's Perry White in Superman, has a small part in the first and final chapter. For plot, there's even less logic than usual: bad guy wants to take over world with an army of invisible soldiers, but can barely manage to keep himself invisible. Overall, below average.