The next challenge for fans of Cain's Jawbone: the TikTok sensation and international bestseller.

A body is found stabbed to death in a locked room. The police find no weapon, no motive and no suspects. However, the murderer has in their possession a box of one hundred cryptic picture postcards which—if properly understood—would explain not just this murder, but nine others. These are those cards.

Readers must rearrange the pages of text to unravel the story and identify the murderer, victim and location for each of the ten murders. They must also consider the separate puzzles presented by the curious images on the other sides. 

Torquemada taught us that complete dedication is key and from devising detective pinboards to daily investigation diaries, Cain’s Jawbone puzzlers did him proud. But now the time has come to dust off that magnifying glass, because a global movement to solve the first picture postcard puzzle is about to begin. Do you have what it takes to explain The Researcher’s First Murder?

• Tweet