A series of arsons shakes downtown Mainz. Two radio messages come in one after the other that night: Garbage cans are burning in residential areas. The flames threaten to spread to the houses. The police have to be on site quickly. The two police commissioners Sarah Schräder and Jonas Horder try to get the fire under control before the fire department arrives. Meanwhile, another garbage can is burning in the neighborhood. The Mainz Fire Devil has been causing mischief for months. When the fire was extinguished, the team from the Mainz 1 Police Department began looking for the perpetrator. Several identity checks are scheduled that night. Meanwhile, the Neustadtwache Mainz team receives a tragic radio message: a man is lying lifeless in a pool of blood. Next to him is a gun. Here, too, the police officers have to be on site quickly and clarify: Is this a crime, a murder or is this a suicide that the patrol officers find?

Quick intervention is required when this radio message comes in: choking attack on an Uber driver. When the police team Sarah Schräder and Jonas Horder arrive at the scene in downtown Mainz, a man has another man under his control. The situation is completely opaque. The team has to react immediately: It turns out that the man lying on the ground is heavily drunk and very aggressive. He's the one who attacked the Uber driver. His friend holds him. The Uber driver complains of severe pain in his neck. Why the choking attack occurred remains unclear. During the night another radio message comes in: A girl is looking for her friend. Both were attacked and beaten by men on the banks of the Rhine. The girls fled in different directions. Now the worry is great: Where is the girlfriend?

A drunk man riots at a gas station in Mainz. The employee calls the police. When the police officers arrived on site with flashing lights, the man continued to behave aggressively and unreasonably. A scuffle ensued until the police handcuffed the man and calmed him down. Meanwhile, the two police commissioners Sarah Schräder and Jonas Horder are still looking for the missing girl on the banks of the Rhine. After an extensive search in the dark, they finally find the distraught girl. She was beaten and needs to be checked in hospital for injuries. There is trouble in front of a club in downtown Mainz. The bouncer called the police because a group of young men were rowdying and behaving aggressively. The patrol team Lena Bottländer and Gerwin Schwiersch have to call for reinforcements; they cannot handle the situation alone.

The 11.11. in Mainz, carnival, state of emergency in the carnival stronghold! Both teams from the Mainz 1 police station are on duty that night. Lena Bottlender and her colleague Gerwin Schwiersch, Sarah Schräder with Jonas Horder. The 11.11. It's a very special night for the four of them, there are a lot of people out and about and many of them are heavily drunk. Crimes, crimes and misdemeanors are increasing. The two patrol teams rush from operation to operation in their police cars with flashing lights. Sarah Schräder and Jonas Horder find themselves in the middle of an argument between a group of young people and an older man. The fact that the latter of all people resists and becomes verbally abusive almost upsets even the otherwise calm duo - and puts the man in police custody. Both teams are called to a burglary - a rather unusual operation on Carnival. At the crime scene, the situation puzzles them.

Winter: The dark season is also the time of burglaries. The team from the permanent criminal service is called to a residential building in Mainz. Burglars stole thousands of euros there and took heirlooms. A traumatic experience for those injured. Not only valuables were stolen by the thieves; The fact that strangers were able to gain access to their own house and ransack everything in the bedroom also leaves those affected traumatized. Do the secured traces lead investigators Melina Reisel and Kevin Gugenheimer from the Criminal Investigation Service (KDD) to the perpetrators? The team Sarah Schräder and Jonas Horder are called to an accident in the city center. The car was pretty much wrecked and the driver got away with a black eye. However, the novice driver was drunk. He must therefore hand over his driving license during the probationary period.

On New Year's Eve the radio message comes in: a break-in at a school. The police arrived quickly on site, but the area was completely unclear in the darkness. When the police officers discover the burglars, a short chase ensues. It turns out that they are teenagers who wanted to have a little adventure. That same night, a car races through a 30 zone, with the two police officers Sebastian Obermeier and Dominik Muders following behind with flashing lights. You provide the driver. As they approach the vehicle, they notice a suspicious smell: marijuana. Examination of the occupants and the vehicle shows that these are not the only drugs they have with them. Meanwhile, the team of Michael Kirch and Paul Wiens is called upon to respond to an accident. The question of guilt is unclear and the statements contradict each other. The police team helps solve the car accident.