They arranged a plan to throw suspicion on John Cavendish, by buying strychnine at the village chemist's, and signing the register in his hand-writing. 
The strychine was not purchased in John Cavendish's name.
mnli hypothesis: The strychine was not purchased in John Cavendish's name. premise: They arranged a plan to throw suspicion on John Cavendish, by buying strychnine at the village chemist's, and signing the register in his hand-writing. 