I consider this to be a rather neglected Universal film simply because it isn't mentioned much and that is too bad because this film really offers a lot.
Coleen Gray stars as a woman married to a doctor who is conducting experiments in order to make people young again. Phillip Terry is Dr. Paul Talbot, an obsessed doctor who wants a divorce from his aging wife, June. The opening confrontation between Gray and Terry sets up the movie perfectly.
Talbot is visited by a very old woman who tells the tale of her African tribe and their youth restoration "magic", so the good doctor cancels his divorce from his wife and takes her with him on the expedition to find the tribe. When they discover the old woman and her people they are shown how the "magic" works as the elderly woman is transformed into a beautiful young woman played by Kim Hamilton.
June finds out why her husband really brought her along and in a rage asks to be granted a night of youthful living. the "magic" the natives use consists of liquid drawn out of the base of the neck of men and June offers her unfaithful husband up as a sacrifice for this night. The natives comply and June is once again young and beautiful. She and the expedition guide (John Van Dreelen) escape to safety.
June starts to turn very old and ugly and kills the guide for his live giving fluid as well. We switch to several months later and June arrives back in the US and seduces her lawyer which makes his girlfriend very jealous. Grant Williams is the lawyer and Gloria Talbott is his girlfriend.
Things get very complicated as the film draws to it's interesting conclusion. I have never been able to figure out why this film is so neglected.
It is available on DVD, so I recommend you see it if you haven't already.