Two men go deep inside the slippery cave, near the ocean. They are in search of a treasure. When a body is found, the strange case of murder is taken to Mr Keen. Especially when the body has disappeared.
His investigation begins with the wife of the missing man, Mrs Ramsey. Is there a love triangle going on? Schemes for a get rich quick plan?
Things take a dangerous turn when the man who first brought the story to Mr Keen turns up dead.
Working with the local police, another potential witness is turned up, and the case develops further. Despite any dangers in the cave, Mr Keen goes to explore the cave for himself.
Listen in to get all the clues for yourself to see if you spot the real killer, and how it was done. Is there really a pirate treasure down in the cave?
Mr Keen has the mystery solved, and arranges for a meeting of the suspects to spring his trap.