To me, this serial is directly inspired by the much superior Captain Marvel serial. There plots are very similar and even share some of the same themes (Captain Marvel had a scorpion theme, this had a scarab theme). In fact, they share some of the same cast. The plots are typical of the era's serials - a mysterious crime syndicate is trying to attain power and the hero is the only thing standing in the way. Very little thought seems to have been given to the series. Even for the day the Captain America costume looks horrible (especially the eye holes). Actor Dick Purcell doesn't do a particularly convincing job in either the roll of Captain America or as Grant Gardner.
The cliffhanger endings end up seeming more like cheats or cheap tricks rather than real, intriguing heart-stoppers. Most of the time, Captain America escapes merely by dumb luck since he has no real super powers.
Captain America is bloodthirst in this serial (which is totally out of character). He often charges into a room, pistol drawn, ready to shoot. Rarely does a villain escape with his life. The police seem to accept this without question. In one scene, Captain America phones the police and tells them to come over right away, he just killed a man. The police respond with "Good job! Go get 'em!" The police seem to be completely helpless at every turn, relying solely on Captain America to solve their problems.
All in all, this serial's greatest failing is not being true to the character of Captain America. It does retain some value as the first time a Marvel character appeared on screen and for that alone it is worth watching.
1LR Review - 6 out of 20 - It's a Failure!