Season 1 of Helmer and Sigurdson premiered on March 21, 1976.

We find ourselves in the Norwegian Broadcasting Company's radio studio for the program Nitimen. Kjell Tue sits as always by the microphone, and in the control room is Totto Osvold. Bank Manager Hugo Oswald is due to be interviewed live on the air, but suddenly dies in his chair, poisoned on live air. Police Investigator Helmer and Sigurdson is put on the case. Pensioner Borckmann, the bank managers neighbor, also involves himself in the investigation.

Season 2 of Helmer and Sigurdson premiered on December 4, 1976.

Secretary Benedicte Holst walks in on Vestre Gravlund, on her way home from work, and disappears without any trace. Helmer and Sigurdson soon gets a murder to deal with. Benedicte is found dead, drugged with ether before being drowned. And, after another woman secretary is reported missing, the Police fears that they are dealing with a serial killer. Can they prevent him murdering again?

Season 3 of Helmer and Sigurdson premiered on November 4, 1977.

During a fight between two burgulars at a gas station, the Policeman Trond Steen, kills one of the burgulars. He gets suspended, and later is fired. He lives together with journalist Henriette Strande, who writes under the pseudonym Nuff. Helmer and Sigurdson gets a new murder case to deal with, and their investigation lead them to the shipowner family Larang, and their former colleague. Their former colleague Trond is seen at the crime scene for two murders, and is now chased by the Police all over the country. If Trond is innocent, can he aquit himself and find the real killer?

Season 4 of Helmer and Sigurdson premiered on December 2, 1977.

Pensioner Brockmann and his friend Agathe Skram is visiting the widow Halvorsen in Tøyengata in Oslo. They are enjoying themselves with their morning coffee and Nitimen on the radio. Sadly their enjoyment is interrupted when they witness a murder when they look out the window in the house across the street. The Police claim the death is due to natural causes, however the retired Investigator Brockmann thinks the death seems suspicious, and does more thorough checks. Soon, Helmer and Sigurdson gets a new murder case to investigate. The clues point to an unknown, mysterious, bald man.

Season 5 of Helmer and Sigurdson premiered on December 28, 1979.

The business man Henrik Lehman and his wife Tove is spending their summer on their country house in Risør. The idyllic setting is broken by a terrible event. An accident, or maybe a crime? Police officer Sigurdson, which by chance is vacationing in the same place, together with his colleague Mette, gets a mystery to solve.

Season 6 of Helmer and Sigurdson premiered on January 30, 1981.

Helmer is out moose hunting with his friend and neighbor Aune in Northern Trøndelag. A member of the hunting party is found shot and killed with Helmer's rifle, and Helmer is suspected of the murder. Helmers wife Aud gets involved in the case, and travels north together with investigator Skagen to solve the murder.

Season 7 of Helmer and Sigurdson premiered on February 27, 1981.

Gas station attendant Ali Reza is as usual finished at work at midnight, to ride the bus home. In the morning he is found dead under a bridge, stabbed in the back with a knife. Helmer and Sigurdson gets put on the case. Has he been a victim of an internal Pakistani conflict? Who can have motives to stab the gas station attendant in the back?

Season 8 of Helmer and Sigurdson premiered on March 20, 1981.

Ruth Vang lives in an old appartment building in downtown Oslo. One morning she comes running out of her appartment, falls in the stairs and lies there unconscious. Two neighbours, Vigdis Myrnes and journalist Per Høøk, comes upon the scene and calls for help. In her appartment, they find the body of the owner of the building, Otto Hagenberg. In the appartment building, the married couple Bergheim and the mysterious man Peter Sand, also lives. Helmer and Sigurdson starts the investigation. The journalist Høøk, who is currently working on a case about slum lords, also becomes interested in the case. Høøk wants to help Ruth Vang's son clear his mothers name, and obtains valuable information, which in the end helps Helmer and Sigurdson clear the case and reveal the murderer.