But I still don't see how he managed to prove his alibi, and yet go to the chemist's shop? Poirot stared at me in surprise. 
Poirot looked at me in disbelief.
mnli hypothesis: Poirot looked at me in disbelief. premise: But I still don't see how he managed to prove his alibi, and yet go to the chemist's shop? Poirot stared at me in surprise. 