Maddie Hayes wakes up to find her staff have quit and all her money has been stolen. One of her few remaining assets is a loss-making investigation agency run by David Addison. She sacks the staff but David is determined to keep it going.
It is Maddie's first day at the Blue Moon Detective Agency but there is nothing to do. In desperation, David 'steals' a client from a rival agency. The man wants them to find his estranged son, but all is not as it seems.
Blue Moon have been hired as security consultants for an aerospace firm from which a rival company has been stealing secrets. Maddie and David work through the rival company's owner and a psychic before they work out what is going on.
A talk radio host is murdered on the air and David thinks it would be great for business if they solved the case. While investigating they find that him and the station manager's wife were having an affair, then they find that he faked his death and is still alive. The plot thicken's when the station manager is murdered.
When Ms. DiPesto has won a competition, she is allowed to join a Murder on the Orient Express (1974) inspired crime game in a train created by her favorite crime author. She is accompanied by Maddie and David to central station. Maddie and David miss to leave the train before it starts off and now have to stay on it since it won't stop for the next 24 hours. When a real murder happens, everybody is suspicious and the two detectives have to solve the crime.
David gets the agency a job collecting money from debtors, which he believes that it will be easy but Maddie is not so sure. They find themselves involved in murder, a disappearing body and an international conspiracy.
When David's brother Richard shows up, he does not only seem to be a rich man, but also makes an impression on Maddie. While David has got to handle his jealousy, Maddie has trouble to pay back her $37 000 debt to the bank. When David is attacked by a stranger, who wants back his money, David realizes that all the money that his brother spends does not belong to him.
A mysterious woman appears in Maddie's and David's agency, who does not want to show her face. She wants Maddie and David to find her former lover, who is the reason why she can't show her face. The two detectives find this man, but find out on the next day that someone murdered him. Of course, the mysterious woman is their very first suspect.
Maddie learns where the accountant who took her money is and is determined to get it back, David tries to talk some sense into her, telling her he is in South America so her money is gone. She won't listen and hopes a plane, she imagines him feeling guilty and apologizing instead he maneuvers he out, and just when she thinks all hope is lost David shows up. With him they win, but if they won some other poor sucker lost, Maddie want's him to be the poor sucker. They get him in a little one on one, $100,000 to start Maddie puts up her house and car. When it comes to the...
When David and Maddie meet the owner of a club who tells them about an unresolved murder. Maddie and David argue about who they think the real murderer is and, in their dreams, set about solving the murder that occurred 40 years ago.
A wealthy woman comes to David and Maddie when her son is kidnapped. They are hired to negotiate the price of the ransom and to get her stepson back safely. Things are further complicated when the stepson is kidnapped a second time.
Maddie is hired to find a silver locket by an old girlfriend of David's. He has strong feelings for her and thinks that her husband is trying to kill her. However, Maddie isn't so sure, especially when she kills her husband in self-defense.
An Irish girl who claims to be a leprechaun wants to hire the Blue moon detective agency to protect her. David is willing to take the case, but Maddie thinks that the girl is mentally ill and needs a psychiatrist, not a detective agency.
An artist, whom Maddie has never met, paints her portrait and then shoots himself. Maddie decides to purchase the portrait and gives it to the artist's brother, who is then killed. It turns out the brother was an international art thief.
A criminal in the witness protection scheme is killed but his wife and baby manage to escape. When fleeing, the baby is left in Agnes' apartment but without any explanation. Maddie and Addison decide to try to find the mother.