It concerns a futuristic medical (doctor's) bag accidentally sent back in time several centuries to the present day, the ethics of such an occurrence, and the turmoil that ensues.
In the future of 2450 A.D., the majority of humanity exhibits reduced intelligence and is unknowingly supervised by a superintelligent minority to maintain the semblance of social normality.
A "physicist" goads his minder into giving him specifications for a time machine, which he uses to send a "doctor" friend's automated medical kit (the titular black bag) into the past.
The patient's eighteen-year-old sister, Angie, discovers the futuristic patent application date on one of the instruments and grasps the financial opportunities.
"The Little Black Bag" was the basis of episodes (using the same title) in three television series: Tales of Tomorrow in 1952, Out of the Unknown in 1969 (which now only exists partially), and Night Gallery in 1970.