Three bullets, a dead man, and £50,000 in insurance. Troubles arise when Dr. Hardy discovers the Unknown Factor.

Penny Goodwin shoots her husband in cold blood and there appears to be no motive. Why she has killed him is far from clear. When Hardy starts an investigation, he uncovers a most ingenious plot which even Fleming will not believe.

Actual causes of death and accurate timing of the death can be essential to a defense in a trial. Dr. Hardy appears as the expert witness for the defense and finds himself opposed by his former professor.

Miss Daley has given up working because her old boss is leaving. She finds out that he is still with the firm and becomes very ill. She goes to see Jo Hardy and tells her that she's convinced she has heart trouble.

A girl is assaulted in a park and the only witness is her young daughter. The police are certain they know who did it, but the girl cannot identify the man in an identity parade.

Mr. Toller is a who has no time for the weak or the idle, without humour. Jo Hardy is treating him, he is arrogant and she patiently tries to diagnose what is causing his illness, which becomes more and more serious.

A woman is found dead by the side of a railway line. Hardy is brought in to help the police. The woman has been murdered, and as they investigate, the police and Hardy realise that they have a dangerous psychopath loose in their area.

An old man dies. When his housekeeper returns some unused tablets to the chemist, suspicion clouds the issue. Dr. Hardy is brought in to conduct various tests and he questions the principals in the case.

A man falls overboard from a ship near Hull and washed ashore dead. Injuries sustained in the water means he is unrecognizable. The most careful planning can go awry and only an expert can interpret the facts with which he is presented.

The death of small children is always tragic. The tragedy is increased by unspoken prejudices and the possibility that one of the parents may be to blame.

The Hardys are enjoying the peace of a summer evening. There is the noise of a shotgun. A man is brought to Dr. Jo's surgery with a non-fatal shotgun wound but John decides that this is a case for the police.

A drunken driver is responsible for the death of his brother-in-law and business partner and for the death of the driver of the second car involved in the accident. Hardy's concern for the facts leads to an exciting conclusion.

A safe is blown. The job has all the trademarks of a known criminal. Fleming pulls in two men in for the crime but forgets he needs concrete information to pin the crime on them both.

Murders take place and each crime is similar to the last. One person must have committed them; but who? Another attack. The victim survives but has amnesia and is the only person who can make an identification. A suspect is arrested.

Hardy is trying to piece together the burnt pieces of paper found in the suspect's room. Jo has been asked to try and break the surviving victim's amnesia by hypnosis. The suspect is questioned at length. The case builds up against him.

Martin Ingram, who has been arrested for assaulting Vivien, stands trial for his alleged crime. He is defended by a brilliant woman Q.C. The result of the trial remains in doubt until almost the last moment.

A smashed lock, a bloodstained jacket, a drifting boat and a takeover bid. Dr. Hardy with the aid of a few bright feathers and silk thread solves the mystery of a disappearing man.

When violent death strikes down a pretty farm girl, Dr Hardy and Inspector Fleming come up against a wall of stubborn reserve. Persistence at last brings Dr Hardy to a 'not inconsiderable suspicion' of the killer's identity. But proof.

Illegitimate babies present problems. Bringing one up in an atmosphere of disapproval can be harder than the alternative. To some, the decision is easy; a matter of practical common sense. To others it's life and death.

A man is found guilty of murdering his wife and sentenced to life imprisonment - could he be innocent? Unquestionably, the facts prove him guilty. Or do they?

Estate Duties - a curse to be avoided? When a businessman is found drowned it could mean ruin for his family.

That little Lucille died a violent death was certain; how she died was more obscure. Dr. Hardy's painstaking research and insistence on accuracy finally establishes the truth.

Protection: you can refuse to pay, you can go to the police for their protection - or you can stand the risk yourself.

A grocer, Harry Kirby, lies dead - poisoned, electrocuted, and gassed. If suicide can be established, surely this is gilding the lily. Why was a large sum of money found laid out neatly beside the body? And if it wasn't suicide.

An old man relies upon his daughter to look after him during convalescence but she has her own life to lead.

A hospital ward is destroyed by fire. Could it be deliberate - and if so, who would want to burn down a hospital and why?

There are classic symptoms of strychnine poisoning when a wealthy landowner dies after eating a trout, freshly caught, the question is who poisoned him? And how?

Jo's car is run off the road by a lorry. The driver may be guilty of dangerous driving. Dr Hardy receives a letter threatening his wife's life and demanding he change his evidence. Hardy refuses but it is at the risk of his wife's life.

Dr. Hardy is involved in tracing a ruthless psychotic killer who is employed by the accused in an attempt to suborn witnesses. He is determined to give his evidence, but the police issue firearms to protect his life.

A doctor may reasonably diagnose a brain tumour as the cause of death of his first wife. But when his second wife dies in similar circumstances and both are known to have been wealthy women.

A woman lies dead in a country road, apparently the victim of a hit-and-run driver. But something doesn't quite fit. She lived in the town. Why would she be in the country at that time - in those shoes? And what about the tyre marks?

A man is shot three times in front of witnesses. When the police arrive there is no body. Has he been shot? Is he really dead?

Eddie spends much of his time in a betting shop. After a win of forty pounds he is found strangled in his own home. His grandson, who lived with him, is missing. Why is he trying to leave the country with forty pounds in his pocket?

While its owner is on holiday an abandoned dog wanders the streets and becomes savage, causing the death of a derelict meths-drinker. Could there be some similarity in the lives of man and dog?

Why should a businessman crash into a bridge support at 80 m.p.h.? When the post-mortem reveals him to have died as a result of the impact, and not from physical causes. What other reason could there be for the accident?

Drug addiction is an increasing problem in our society. In the first episode of a two-part story, the hopelessness of the addict is matched against the efforts of doctors to control the terrible effect of the drug.

It is said that drug addicts make poor parents. How do a young couple, both of whom are addicts, cope with attending to the needs of their small baby?

Once a man suspects that his 10-year-old son is not in fact his, he cannot rest until he has discovered the truth.

Threatening suicide is often a cry for help, sometimes that cry is heeded, sometimes assistance is too late.

The body of a student is found in a pig-fattening shed. Hardy has to establish the cause of death.

The body of an attractive young girl is found by the roadside. Who was she? How did she get there? How did she die? Hardy and Fleming are faced with finding the answer.

Fleming and Hardy are used to hit-and-run cases where they find a body but no car. In this curious case the situation is reversed: a blood-stained car but no body.

Gypsies led by Samuel Brown arrive in the Hardy neighbourhood - to the horror of many residents. A public meeting is called to discuss the 'problem.' But protest can go too far.

After fifteen years of childless marriage, Ruth Fletcher has a son. But she has a problem which she takes to Jo Hardy: is it possible that her husband is not the father?

Dr Hardy has told Harry Fletcher that he could not be the father of his wife's child. Harry confronts his wife's lover, Michael Jackson.

Cedric Lambert, a lonely 54-year-old bachelor, visits Dr Jo Hardy in her surgery. But apparently there is nothing wrong with his health - all he wishes to do is to show her an antique book.

Hardy is much possessed by the problems surrounding the scientific fact of death. And in this story of an elderly retired Major, his wife and son, the police become totally involved as well.

Early one morning a young Maltese girl is found stabbed to death. Fleming is immediately convinced that her ex-boyfriend is guilty. Hardy has other ideas.

A young librarian finds a body in the woods. He does not tell the Police but the Press - which for Hardy and Fleming adds confusion to an already confusing case.

The milkman pays his morning call on Mrs Carr, and finds her lying unconscious on the conservatory floor. She is surrounded by fragments of a milk bottle - which lead to several sleepless nights for Hardy and Sandra.

Two young boys have their day's fishing disturbed when they find a body in the river. The question facing Fleming and Hardy: did he fall or was he pushed?

In the last of this series, Hardy and Fleming are faced with the kidnapping of a son of wealthy parents - not so unusual for them but strange and unfortunate for Jo when she becomes involved.