Twenty-Fourth Level — Kenneth Benton

When Peter Craig stopped off in Rio for a few days, he triggered off a series of bizarre events. Craig had been asked to make unofficial enquiries about some highly interesting coloured diamonds emanating from Brazil. Why was the secret of these few pale stone so precious that Graben, the superintendent of a gold-mine, would kill, again and again, to preserve it? Craig decides to act and follows Graben up-country where Craig and wealthy socialite Alcidia find themselves trapped in the twenty-fourth level of the mine, with only their courage between them and death.