Inspector Leo Bäume (Vladimir Burlakov) is called to a crime scene: a woman is found dead in her villa, the suspected burglar is lying on the ground, seriously injured. At the same time his colleague Adam Schürk (Daniel Sträßer) is called to his father. He is found dead shortly thereafter. Shot with Schürk's service weapon. The inspector is therefore considered the main suspect and is sent to the Saarbrücken JVA, where as a police officer he doesn't have much to laugh about. Meanwhile, his friend and colleague Bäumer tries to prove his innocence - even if everything speaks against him.

The completed episodes of the new Saarbrücken investigators Adam Schürk (Daniel Sträßer) and Leo Bäumer had a horizontal narrative thread from the start. Both have in common a terrible act from their youth: Woods knocked Schürk's father unconscious at the time, who then fell into a coma. Both then covered up the crime with a fire. This story comes to an end with "The Heart of the Serpent".

Unfortunately, it is not uncommon for a "crime scene" inspector to be suspected of murder in the crime series. It is clear to the viewer in advance that the perpetrator must be someone else. This time, too, it is the friend and colleague who is the only one who initially believes in innocence and ultimately confronts the real culprit.

In the previous two "Tatort" episodes from Saarbrücken, the two male investigators Schürk and Holzer were in the foreground. This time, her colleagues Esther Baumann (Brigitte Urhausen) and Pia Heinrich (Ines Marie Westernströer) can distinguish themselves: Without their help, the case would not have been resolved in the end. "The Heart of the Snake" could be an indication of the future of the team: It should be much more female in the future.

The story is a little bit tired, but the implementation is exciting: a "crime scene" worth seeing.

In the following cases, Commissioners Schurz and Hoelzer determined: