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. 
He failed dismally to prove his alibi.
mnli hypothesis: He failed dismally to prove his alibi. 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. 