Bassie & Adriaan are in Rotterdam and receive a letter
Bassie & Adriaan: De Geheimzinnige opdracht
Bassie & Adriaan received a letter from the Mysterious Client to come to Rotterdam. When they have arrived in Rotterdam they receive a letter from a girl from the Mysterious Client and the letter says that they have to go to Germany to look for the next package.
The recording was recorded at the Parkhaven near the Euromast in Rotterdam.