Published in Detective Comics #18, August, 1938, 8 pages.
Out on a date, Sally Norris is certain that Bart Regan, who says he is tired of chasing spies, is ready to propose (again) but then a call from the Chief takes him away. The mission is to find the stolen Kahoon Ruby, a gem worth a fortune but with a horrible legacy about it.
Spoiler Alert: Regan proposes at the end.