Crime team Siri and Max are back, on a case which calls for all their resources of ingenuity, courage, climbing ability and code-breaking talent.

A motorcycle gang has occupied the once so peaceful town of Heimvik. The first prize for the big chess tournament has been stolen from the safe in the town hall. And on top of all that, Max is being followed by a mysterious rival who calls himself 'The Masterbrain.' Have Heimvik's young detectives bitten off more than they can chew?