Tanking on the way home Heldt is just in time to control an exploding amateur bomb brought into the station by state of the art robot. *Grün fearing a test run, he and prosecutor Bannenberg focus on a lead to chemistry student Alan Barsani, who has a geocaching game alibi. Heldt believes it and makes a mode cars racing circuit friend, car crash-crippled Manuel Unterberg. Other club members like dubious cleaning firm manager Dierk Jager also make plausible suspects, but Heldt must face his buddy's accident's tragic shadow back to his single mother's home where he was forced to move back in due to his wheelchair.