Bull-Dog Drummond's Third Round by Sapper

Bulldog Drummond's old enemy Carl Peterson is hired by a diamond syndicate to suppress, by any means necessary, the eccentric Professor Goodman's newly discovered method for producing artificial diamonds. While accepting the syndicate's money, Peterson secretly plans to obtain the method for his own use. Drummond is drawn into the matter because his friend Algy Longworth happens to be engaged to the professor's daughter.