Mrs. Cavendish administered a safe, but effectual, narcotic to both Mrs. Inglethorp and Mademoiselle Cynthia. 
Mrs. Inglethorp gave the narcotic to Mademoiselle Cynthia. 
mnli hypothesis: Mrs. Inglethorp gave the narcotic to Mademoiselle Cynthia.  premise: Mrs. Cavendish administered a safe, but effectual, narcotic to both Mrs. Inglethorp and Mademoiselle Cynthia. 