A man bids farewell to his home; Mine subsidence has made it uninhabitable. Meanwhile, the Saarbrücken detective team headed by Chief Inspector Franz Kappl (Maximilian Brückner) is on a new murder investigation. In the head of the young miner's wife Wiebke Steinmetz, who was found dead, there is an iron - part of the traditional miner's tool. Very appropriate in this environment, one of many mining settlements in the Saarland where the mood is depressed. The end of mining has come, the closing of the last pit is imminent. With an underground event, the Karlsgrube is supposed to deliver the symbolic last wagon of coal and then close it. String trio, speeches and cold buffet on sole eight – a joke, the miners think.
Three crosses, the main thing is that the pit closes, think those who have been damaged by mining, whose houses the mountain is throwing out of balance. 'Tatort' inspectors Franz Kappl and Stefan Deininger (Gregor Weber) stay out of the conflict that pits fathers and sons, daughters and mothers against each other. They investigate in all directions. Franz Kappl experienced the mining environment up close for the first time. Terms such as mountain or weather have so far tended to evoke tourist associations in the young man from Bavaria. Now he learns firsthand that they can mean deadly danger. When an explosion buried all entrances and exits underground during the ceremony, Kappl was right in the middle of it and got to know the discussion about structural change and mining damage from a completely different perspective.
And yet he has to keep cold blood when a murderer is also around at a depth of 1200 meters. While his colleagues spend days chasing after the man who suspected Wiebke Steinmetz's murder, the operation to rescue the celebratory meeting buried underground is taking longer than planned. The air, which is called weather in miners' jargon, is running out - a fight against the clock begins.