A man falls from the top floor of a luxury hotel in Vienna. The Iranian diplomat and nuclear physicist Dr. Bansari apparently committed suicide. But why did he buy expensive opera tickets for the same evening? Moritz Eisner and his colleague Bibi Fellner want to investigate the matter, but the Iranian embassy and the Austrian Foreign Ministry immediately get involved.

The case is subject to the strictest secrecy - the dead man's laptop and cell phone are confiscated. The two investigators are annoyed, but do not give up. The hotel's surveillance video leads them to the trail of the shady lobbyist Johannes Leopold Trachtenfels-Lissé. He has arranged a secret deal with Dr. Bansari.

Eisner and Fellner find out that the case involves valves and pumps that are needed for nuclear reactors. A trainload of the high-quality components is to be sent to Iran via third countries. For the two investigators, a race against time begins - and against the Israeli secret service Mossad.