Younger viewers are spending less and less time watching TV. They prefer to surf the Web. The task: to give the young audience a thrilling detective experience and generate enthusiasm for the ZDF crime series. The solution: a gripping crime drama in online displays. For this purpose, we gave cookies a whole new function: users didn't have to click their way through to the next clue, instead we kept tracking them on major websites for one week by using retargeting. Our online detectives then followed clues, cracked mobile phone codes – and ultimately solved the case. Starting at 43 % the interaction rate increased to 80 % on the last three clues.