Hellish summer

It's summer and it's terribly hot. Juncker remains in Sandsted after his father's death and is not doing well. The body of a local lawyer is found in the park and Juncker starts investigating. It turns out that not only did he know the dead man, but he also learns more about his father.

His wife Charlotte, investigative journalist, gets an anonymous tip, which suggests that the terrorist attack in Copenhagen, that ruined Christmas cheer in Denmark six months ago, could have been avoided. Charlotte smells a good story, so she turns to her husband who investigated the case. Juncker knows what happened then, but he doesn't want to help the woman because he feels it could put them both in danger.

Eventually, Signe, Juncker's former partner, who was also involved in the investigation but, unlike Juncker, feels that the truth needs to be uncovered. The two women start to investigate and get into dramatic situations.

The Infernal Summer is loosely based on the first case of the series about Martin Junckersen and Signe Kristiansen, The Hard Winter.