They are hired by J. Westly Arnold (Emmett Vogan) to fly an inventor, Dr. Tobor (John Merton), to his secret laboratory, where he is working on a new and powerful energy machine.

A mysterious villain named "The Chief Pilot" (Wheeler Oakman), however, is also determined to have the new energy machine for his own purposes.

Hop and Tank, aided by Gail Nolan (Jennifer Holt) and her younger brother, Jackie (Robert "Buzz" Henry), finally overcome the criminals only find a bigger threat to them all within their group.

[6] The aircraft in Hop Harrigan included a Boeing-Stearman Kaydet, Bellanca Cruisair and a Stinson Junior.

[7] Author and film critic, Andrew C. Cline wrote in In the Nick of Time (1984) that Hop Harrigan is fairly action-filled serial, with well paced action.