Bulldog Drummond's Secret Police (1939) on Netflix

Plot summary

Captain Bulldog Drummond and his fiancée Phyllis Clavering have put off their wedding for a long time, and Temple Tower, his ancestral home, is where they mean to hold it. He is busy with the arrangements when the absent-minded Professor Downie calls on him there. Downie reports that a fortune was buried in a walled-off storeroom beneath the estate, and that he owns a book written in code which would lead whoever holds it to the hiding place. Someone else wants the riches too, and the code book is stolen. Drummond is drawn into the affair in Rockingham, twenty-eight miles from London.