John Ridgefield is the self-made wealthy owner of the Ridgefield Aircraft factory. The far-seeing aviation manufacturer is driven toward a significant breakthrough, envisioning a plane that can fly faster than the speed of sound.
During the war, his daughter, WAAF officer Susan Ridgefield, marries Tony Garthwaite, a young fighter pilot, and brings him home to meet her family. Susan's brother, Christopher, is about the make his first solo flight. Anxious to please his domineering father, Christopher loses his nerve and is killed when the plane crashes.
After the war, Susan's father offers Tony a job as a test pilot for the new jet airplane he is developing. Susan is dismayed when Tony accepts. She blames her father for Christopher's death and cannot understand the devotion of both her father and her husband to experi-mentation with airplanes. She desperately attempts to dissuade
Tony from testing the plane which Ridgefield hopes will break the sound bufier. Tony enthusiastically insists. He dies in the final test when the plane disintegrates on reaching the speed of sound.
Aghast at her father's continued obsession despite the risk to human life, Susan leaves her father's home. Her baby is born at the home of another pilot, Philip Peel, and his wife. The aircraft is again rebuilt, and Ridgefield asks Philip Peel to test it. When Susan perceives her father's personal torment while "sweating out" the time of yet another test flight, she begins to understand the dedication to discovery that drives him on. The test is successful as the plane piloted by Peel breaks through the sound harrier. Susan and her father are reconciled, and she and her child return home.