A film projectionist longs to be a detective, and puts his meager skills to work when he is framed by a rival for stealing his girlfriend's father's pocketwatch.

The third in a series of films featuring François Truffaut's alter-ego, Antoine Doinel, the story resumes with Antoine being discharged from military service. His sweetheart Christine's father lands Antoine a job as a security guard, which he promptly loses. Stumbling into a position assisting a private detective, Antoine falls for his employers' seductive wife, Fabienne, and finds that he must choose between the older woman and Christine.

Private detectives Inés, Eva, and Carmen often invade others' privacy but are clueless about confronting their own secrets. While on the job, these three surveillance specialists will have to cross the thin line dividing public and private matters, bringing their own issues to light in order to solve more than just their professional cases.

Mystery writer Cornelia Van Gorder has rented a country house called "The Oaks", which not long ago was the scene of some murders committed by a strange and violent criminal known as "The Bat". Meanwhile, the house's owner, bank president John Fleming, has recently embezzled one million dollars in securities and has hidden the proceeds in the house, but is killed before he can retrieve it.

Teenagers try to clear a friend accused of murder.

Yuzuru Hamura is a university student and a fan of mystery novels. Against his will, he was forced to join the school's mystery club. The club is led by Kyosuke Akechi. Meanwhile, Hiruko Kenzaki appears in front of them. She attends the same university and she is also a private detective. These 3 people attend a summer camp and stay at Shijinso pension in the mountains. On their first day there, they must barricade themselves in the pension. The next morning, they discover a murder has taken place in the pension.

During a visit to childhood friend Edith, retired housewife Hetty Wainthropp discovers that Edith's husband, Frank, has a son by a previous marriage. Hetty decides to turn amateur detective to trace him. When this gives her a taste for detection, Hetty decides to set up a private detective agency.

Set in San Francisco, Jonathan and Jennifer Hart are faced with the prospect of being reunited with Jonathan's long lost sister, and her nephew. Is it possible that Jonathan will finally discover a key to his past or will the "family" turn out to be after something, putting Jonathan and Jennifer in danger's past one more time?

The Harts find themselves in the middle of a dangerous murder plot, but it isn't clear if the plot it a famous author's fictional murder-mystery, or an actual murder plot, until Jonathan finds himself the unsuspecting target of a killer. It begins to look like the culprit behind the plot is an old friend, Frank Crane, but there may be a connection to a corporate takeover of Hart Industries as well.

While making his nightly rounds in the neighborhood, Patti's pet cat D.C. finds himself the carrier of a call for help from a kidnap victim. Patti enlists skeptical law enforcement help to find the victim before it's too late.

On a mission of mercy, Jennifer Hart is in Germany to donate bone marrow to Maximilian, a young leukemia patient. Following the operation, she plans to spend a romantic anniversary in Munich with her husband Jonathan. The bone marrow clinic's director, Peter Donner, is surprised by Jennifer's uncanny resemblance to his French fiancée, Simone Grohe. When she goes missing, Jennifer steps in to play the role of Simone to save Peter the embarrassment of an explanation to his cousin and benefactor Karl von Ostenberg at the lavish engagement party. But, of course, it is Karl who kidnapped Simone - in order to control the fate of Peter's inheritance - and now Jennifer is in as much danger as Simone! Once again the Harts tackle danger and mystery with their usual devil-may-care charm and romance

Ronnie Jackson is a lowly baby photographer who secretly fantasizes about being a private detective. When a lovely baroness actually mistakes him for one and asks him to help locate her missing husband, Baron Montay, Ronnie finds himself agreeing. Several days later he is on death row whiling away the hours until his execution by recounting to a group of reporters the bizarre tale of how he ended up there.