Widowed psychiatrist Roger Corder runs his Harley Street practice with young assistant Jimmy and devoted secretary Nancy, as well as bringing up his precocious young daughter. When the managing director of a large business dies suddenly, there are two likely candidates, Phillips and Hunter, as his replacements. Dr. Corder is called in to assess which is the more suitable.
Danny Pace is a successful pop singer and recording artist. His career is beginning to suffer however as he is convinced that he can see his doppelganger and that somebody is out to sabotage him. Laurie Winters, his manager, refers him to Dr Corder.
Frank Hewitt comes to Dr Corder suffering from amnesia. He is a very religious man, whereas his wife Erica is considerably more liberated sexually. Dr Corder has to unlock Frank's mind to discover what was the dreadful deed he committed and what caused it.
Verity Clarke is an exceptionally talented teenaged ice skater and there are high hopes for in the medal winning class. However she feels that her overly ambitious family is pushing her beyond her limits and she is soon in need of help from Dr. Corder.
Because her husband, company director Henry, stays out until all hours and sometimes never returns until the next morning Julia Gray is convinced that he is cheating on her and attempts suicide. She is treated by Dr. Corder, who discovers that Henry may not have a mistress but he is certainly not as staid as he first appears.
Career soldier Sergeant-Major Bennett is being court-martialled and Dr. Corder has to write an assessment report on this seemingly cocksure man. However events seem to suggest that it is Bennett's commanding officer, Lieutenant Gray, who is the paranoid one and in the course of his investigation Corder exposes an enemy agent.
Given that she leads a comfortable life-style, lacking for nothing, Lady Shaw is one of the last people one would expect to be caught shop-lifting. However, when reports are called for and she gets to meet Dr. Corder it becomes evident that to some extent her uncharacteristic behaviour is a means of rebelling against her controlling husband, a severe High Court judge.
Penny and David Branch are a young couple who seem to be living beyond their means. Penny claims that she has inherited a legacy to fund their life-style but when she is referred to Dr Corder he discovers that she has a life kept secret from her husband to afford their creature comforts.
The two-edged sword is a reference to hypnotism and the fact that it can produce good or bad effects. In the case of Fay Bridges who, years earlier was hypnotised by a quack doctor, it has had a lasting unfortunate effect in her relationship with her husband. Dr. Corder, however, is able to use it to the good in the case of Doreen Stokes in helping her come to terms with the baby she has rejected.
Wealthy Geoffrey Petlen is married to the much younger Eleanor, on whom he dotes. One day she takes a shot-gun and blasts the swans on his lake. She confesses to being prone to unhealthy compulsions, as a result of which Geoffrey refers her to Dr Corder. What he does not realise is that she has met Corder before and has her own, unhealthy agenda for seeing him again.
Dr. Corder is called in to assess Bert Morgan, a young burglar. Not only does he feel compelled to break in to houses with gable but, once inside, he is obsessed with winding up the clocks in the room. Corder, going against the police view that Bert is mad, discovers the key to his odd behaviour is a wartime incident of twenty years earlier.
Jan and Rita Zapotski are a young couple who are still living with both of their sets of parents, a situation which is taking its toll on Jan, who feels frustrated and emasculated as a result. He starts smashing windows to draw attention to his discontent. It is down to Dr. Corder to sort him out, to find out his underlying motives and point him to a happy future in which he can be a master in his own house.
Following the highly successful trial flight of a new aeroplane test pilot Mike Barclay flies the plane off the radar and seems to deliberately crash it into a field. His boss is concerned that this may have been a suicide attempt and Dr. Corder is called in to assess Mike and his home life.