hant return to Britain's adventuring detective, Sexton Blake! His first published novel restored, revised, expanded... and presented with a brand new prequel story!

A deep sea mission...

A baffling murder...

Beneath a sky of limpid sapphire blue, the research ship Gorgon rolls gently on the scintillating waters of the Caribbean Sea.

Below, two men in a bathysphere, lowered more than a 150 fathoms into the crushing depths. But when the sphere is raised, there is only one man inside... and he has a knife in his back!

Now Sexton Blake must answer an impossible question: How did the killer escape?