Brussels, Gare du Midi/Zuidstation, 1973. Architects busy building the Brussels of the future discover a mysterious artefact buried under the station. It holds a powerful secret, known only to a handful of insiders, which will help unleash their creativity. Fearing that the artefact could fall into the wrong hands, they hide clues in the façades of the buildings, discernible only to the trained eye. But watch out! Rival architects wanting its power for themselves have dispatched detectives to find the artefact. Will you manage to track it down in time?