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.