Martin Koslowski (Sönke Möhring) and Hasan Haferkamp (Tim Seyfi) are best friends living in Bochum-Hamme. However, things haven't exactly been going well for them lately. Martin has just been left without warning by his wife, Sylvia, after seven years of marriage, and to make matters worse, the armored truck they drive - diamonds and all - is stolen right out from under them. Not only do they lose their jobs, but they also become the prime suspects in the case. Now, they must launch their own investigation to prove their innocence. They receive support from traffic warden Tina Möller, who has always seen herself as a would-be detective anyway. After some initial success, Martin, Hasan, and Tina decide to strike out on their own and found the "Koslowski & Haferkamp" detective agency.