While protesting against the influx of new economic migrants, the group is in search of the legendary treasure of King Arthur and his famous sword, Excalibur. Blake is then sent to the site to dismantle the organization and prevent the sad plan of their leader, a certain "Grand Druid". At the same time, at the Center of Scientific and Industrial Research in London, Professor Mortimer presents one of his new revolutionary inventions: a pocket excavator, "La Taupe". To test the resistance of this technological prowess, the British press announces that "La Taupe" will be sent to the Cornwalls. In this new album, Blake and Mortimer have to foil the attacks of an independant group with the help of an inescapable and for the least unexpected... Colonel Olrik himself! But can we ever trust a "friend" of this acabit?