Dr. John Brady is working at the Castle Hill government laboratory investigating the nature of refraction - his experiments achieve success when he is able to make a rat become invisible - but a leak in the containment chamber releases the radation into the lab, and Brady finds himself rendered completely invisible as well. At first put under lock and key by the government, he escapes and runs to his former colleague Dr. Crompton for help, but finds that the powers of invisibility have the potential to corrupt... The first episode begins very quickly, with Brady becoming invisible in the first moments. Fortunately they give time to introduce and develop Brady and his family before the action starts - already however, the 25 minute runtimes of these episodes starts to show itself, and the pacing does seem a little rushed.

When a British agent is captured in a hostile Middle Eastern country, the government fear that his knowledge of the resistance movement there could place all its members in jeopardy. They call on Brady to rescue the agent from a tightly guarded military hospital. The second episode of the series sets the tone for many of the following entries, with Brady being called on to help someone in trouble. In this case, unlike some of the later episodes, they give Brady a convincing reason to get involved, and makes full use of his invisibility. One of the best episodes.

Brady is working hard to find a cure for his invisibility but needs a human volunteer. He is tricked into travelling to the house of the exiled South American industrialist Raphael Constantine. Hideously scarred by a grenade the man appeals to Brady to use him in the experiments as he yearns for invisibility. However, it soon becomes clear that Constantine has a more sinister purpose in mind for his powers...

An outspoken Russian scientist speaking in London is kidnapped by secret agents and locked up in the embassy. Brady follows her and breaks into the embassy before beginning a diplomatic attempt to have her freed. When this fails he sneaks her out of the building to his own house, but finds that the Russian ambassador is not going to give up the chase easily...

After a serious car accident witnessed by many people, the government reveal Brady's invisibility to the press and he becomes a near-celebrity figure hounded by the media. Meanwhile the friend of his young niece begins to suspect that her stepfather is planning to murder her mother for the inheritance and pleads with Brady to help...

Barbara Crane, a respected theatre actress, finds herself the subject of bribery after accidentally running down a man on a clifftop road. Worried by the events she starts to perform badly, and a suspicious Brady decides to investigate further, discovering that there is more than simple blackmail going on...

A Russian sailor makes a bid for freedom from a trawler at anchor in a British harbour, but is soon captured and taken back to the ship. The head of the refugee committee appeals to Brady to help them and although reluctant to assist, he soon decides to sneak on board the ship and find out what he can do to help - however, it soon turns out that Brady has been set up, and he is ambushed by the sailors as the ship heads back towards Russia.

A group of criminals raid an important British atomic laboratory and photograph some key documents onto microfilm. When the customs officers quickly clamp down on passengers leaving the country, one of the men hides the film in the mink coat of the ventriloquist performer Penny Page who is flying to Paris. When Brady's sister Diane witnesses this, the pair find themselves drawn into a deadly game as the criminals try to get the invaluable film back from Mrs Page.

When an airline pilot is framed for importing drugs into the country, he phones his old friend Peter Brady for help. Before Brady arrives however, the pilot is shot and badly injured in front of his wife, who is blind. Brady helps the police with their investigations and devises and elaborate plot to find the killer...

When the reformed career criminal is framed for an armed robbery and sent to prison again, he is determined to get free and prove his innocence and escapes 5 times before being recaptured. Curious about the story, Brady decides to investigate and helps the man to escape again to discover the truth behind the conviction...

Brady's fame leads to trouble when a group of criminals kidnap his young niece and hold her hostage - forcing Brady to commit a bank robbery.

When one of Brady's colleagues announces that he will not be returning from his holiday in Italy, and is seen using his mathematical talents to win at roulette, Brady decides to fly out and convince him to return - but he soon discovers that Professor Owens is working to save his daughter who is being held hostage by the mob...

After his bag of documents was stolen, Brady is kidnapped by a mysterious man who wants him to commit a murder - and to keep the unseen Brady in check, he has a vicious guard dog who can sniff out and catch even an invisible man.

During an airborne test of an experimental airplane fuel flow controller, something goes wrong and the plane crashes, killing the test pilot. The forth failure in a row leads to public hounding of the project's leader, Scott, and he plans to abandon it. However, his old friend Peter Brady suspects that there might be sabotage to blame...

A young woman named Ellen Summer escapes from a private asylum and runs into Brady on a train, begging him to help her, she claims to have evidence that could save an innocent man who is sentenced to hang for a murder he did not commit. Skeptical at first, Brady decides to meet with the man himself, and when they both tell the same story, he decides to investigate further...

After some important scientific research is stolen, Brady is sent to Amsterdam to identify it after its recovery, but when the British agent is captured by local police, Brady himself has to find the papers and save the agent from jail.

When an outspoken Russian writer is detained at the country's frontier while on the way to a major awards ceremony, Brady decides to cross the border himself and let her out, but he quickly runs afoul of the local military commander...

When a scientist at Brady's lab suddenly burns all of his papers and runs away, Brady sets out to investigate and discovers that he wasn't entirely acting of his own accord.

Toni Trent, one half of a pair of twins and a popular double-act, performing for the troops on a USO tour of Britain finds herself in trouble when she witnesses a killing, and is kidnapped. When her sister Terry arrives in the country and finds Toni gone, she looks to Peter Brady to help.

A UN inspection fails to find the suppliers selling weapons to terrorists operating in the Middle East, however the British representitive Zena Flemming suspects that she might be able to find more evidence if she heads back alone, but takes Peter Brady with her for protection, and as a second pair of eyes.

A young woman walking through a park in France discovers a rabbit that materialises in front of her. Taking it to the government in Paris, they are concerned that it could represent unofficial scientific research and call in Peter Brady from London to take a look at the creature and discover if it could really have been invisible. Heading down to where the creature was found, he discovers a sinister project...

Brady is tricked at a Paris airport, and has his bag and passport stolen - a criminal disguised as Brady uses his passport to travel across to England with a suitcase full of cocaine. Annoyed at this, Brady offers to help the police track down the dealers in London.

In a small Middle Eastern country, the head of the army presents a plan to the King to exploit their position as friends of the major Eastern and Western powers to blackmail major governments. The King refuses to sign and is shot dead, his younger brother, Prince Jonetta is attending a science lecture at his University in Oxford when he learns the news. Brady was presenting the lecture, and decides to sneak aboard as Jonetta travels back home, suspecting there might be trouble...

After loosing big at gambling, Smith, the transport officer at Castle Hill is offered a large amount of money to leak the departure time of a major new experimental rocket section that is being driven up to Scotland for testing. The shipment is hijacked, and Peter Brady who worked on it, sets out to track it down.

Military scientists have been working on a new form of explosive mine containing a light sensitive cell (designed by Peter Brady), that will detonate when a shadow passes over it. During testing there is an accident and an officer is trapped in a pit next to the mine, unable to move. With only a few minutes before the edge of the pit casts a shadow over the sensor, they call the only man in the world who could get to the mine without casting a shadow...

After a plane crashes on arrival at a British airport leaving no survivors, the investigators discover that a component for an atomic bomb had been hidden inside some of the baggage. They suspect that individuals might be planning to plant a bomb under London and begin the search for a replacement piece that would probably be on its way.