This was the second episode filmed, but was temporarily tabled, and was inserted as the 5th episode of the series. All other episodes aired in the order they were shot.
First appearance of U.S. Attorney Ginger Breakstone.
The underwater scenes were filmed at Paramount Studios tank studio. That same studio where "Top Secret!" Underwater bar fight scene was filmed
As Brisco walks into the hideout you can see what looks to be radial tire tracks mixed in with the footprints. The Radial Tire wasn't invented until 1915.