An elegant young Lebanese man, carrying diamonds in his bag, is on the train from Frankfurt to Basel - a drug mule on the return journey. At Basel train station, Hunkeler is waiting for him after a tipoff from the German police, but the courier first manages to flush the stones down the public toilet. Erdogan, a young Turkish sewage worker, finds them in the pipes under the station. To him they mean wealth and the small hotel he always wanted to buy near his family village. To his Swiss girlfriend Erika, the jewels signify the end of their life together. She knows that Erdogan has a wife and children in Turkey. For the courier, finding the stones is a matter of life and death. His employers are on their way to "tidy things up". For Hunkeler the diamonds are the key to finding the people behind the drug deal. They turn out to include, not only the bottom-feeding criminal gangs, but bankers and politicians very high up the Basel food chain. Die Jagd nach Diamanten, Erlös der Drogenmafia, hält den Basler Kommissar Hunkeler in Atem. Ein libanesischer Kurier entledigt sich seiner Ware, bevor die Polizei zugreifen kann. Gefunden werden die Diamanten von einem Kanalarbeiter, der das ihm zugefallene Glück nicht mehr hergeben will. Doch der Kurier setzt alles daran, sie zurückzuerobern ...