An ominous rumbling sound came from further up the tunnel.
"I have a bad feeling about this," said Brunnhilde.
Colorado Smith consulted his notebook. "Our presence has set in motion the Bonecrusher. We must be close to finding the hoard of diamonds buried within the skull of Duggery!"
As the rumbling increased to an ear-shattering roar, Brunnhilde caught sight of a enormous cylinder of rock rolling towards them, supported by massive iron wheels.
"According to this map," said Smith, oblivious to impending doom, "the diamonds are buried in one of the chambers of the skull-shaped tomb of the Duggery clan, along this passage—"
"We're going to be crushed!" wailed Brunnhilde.
Smith looked up. He pushed Brunnhilde into a dense tangle of cobwebs hanging on one wall. She found herself in a shallow niche. Smith joined her as the Bonecrusher clattered past.
Returning to the tunnel, they followed it and found themselves in a vast underground cavern. At its centre was a stone tomb. Smith pulled out his battered notebook and looked at the map.
"The Duggery druids only entered the treasure chamber after a ceremonial procession," said Smith, "in which they passed exactly once through every doorway in the tomb."
"Does the map give their route?" said Brunnhilde, hopefully.
"No—and part of it has been eaten by army ants," said Smith. "But we don't need to follow the druids' route if we can work out which is the treasure chamber ourselves."
Which chamber holds the diamonds?
Prospect invites you to solve the puzzle and send us the solution. Correct answers will be entered into a draw. The winner will receive a copy of Lewis Carroll in Numberland: His Fantastical Mathematical Logical Life by Robin Wilson (Allen Lane, £16.99).
Send answers to info@prospect-magazine.co.uk by 17th July. The winner will be announced in our August issue.
