The |Yellow Mark| is a criminal that has London enthralled in his exploits: holding up the Bank of England, robbing the imperial crown and many more. The Home Office asks Captain Francis Blake to discover the identity of the man who hides behind the Yellow Mark. Blake immediately calls upon his old friend, Professor Philip Mortimer, to help him unmask this mysterious criminal.
Born of Edgar Pierre Jacobs' imagination during the post-WWII period, Professor Philip Mortimer, nuclear physicist, and Captain Francis Blake, dashing head of MI5, are legendary heroes of the 9th art. The author, a close relative of Herge, appreciated the excessive and the astonishing that could be found within the scope of scientific invention; his heroes, very much ahead of their time, discover extraordinary objects and phenomena through their uncommon adventures. Before devoting himself exclusively to them, Edgar Pierre Jacobs collaborated with Herge and took part in the realization of 'Tintin in the Congo', 'Tintin in America', 'The Blue Lotus', 'King Ottokar's Sceptre', 'The Seven Crystal Balls', and the 'Prisoners of the Sun'.