There is nothing that can compromise him in any way, since it is Miss Howard who has the strychnine, which, after all, is only wanted as a blind to throw suspicion on John Cavendish. 
John Cavendish is investigating Miss Howard.
mnli hypothesis: John Cavendish is investigating Miss Howard. premise: There is nothing that can compromise him in any way, since it is Miss Howard who has the strychnine, which, after all, is only wanted as a blind to throw suspicion on John Cavendish. 