It must have been quite twenty minutes before Poirot rejoined me. 
Poirot rejoined me after twenty minutes.
Twenty minutes later, there was still no sign of Poirot.
No one ever knew what Japp was thinking because his facial expression never changed.
Tua Sai Yeahwas a general during the 19th century.
We are looking for her because of that.
Tuppence did not remain silent, he shouted instead.
A man and a little boy fighting.
Youngsters are conversing and learning new things in class.