The Adventure of the Western Star tells the tale of twin precious stones, the Star of the East and the Western Star. The Western Star resides belongs to Lady Yardley in England, while the Star of the East belongs to a famous film actress.  When one of the stones is stolen, Poirot must solve the mystery of the jewels. 

In The Adventure of The Cheap Flat, Poirot turns his impressive little grey cells to the problem of why a particular couple is tenanting a flat at far less than market value.