The case opens on the Alter Markt and the route runs past Museum Ludwig to the Kölner Dom, with the entire game played within a few hundred metres of the cathedral.

You'll be playing a detective game on foot: crack codes, take photographs, and question digital characters whose statements do not always line up.

Every puzzle solved narrows the suspect list. There's no guide and no fixed start time, so you can take your time and even break for lunch without losing your progress.