I also read his first case just before this because Poirot is first introduced to the world in the same location as this story. It's a fitting ending.
Once again Poirot is back at Styles. He knows a murderer is on the premise, but he's not sure who the murderer is. He calls Hastings to join him as his eyes and ears to provide the clues he needs before the person kills again. Hastings is frustrated that Poirot will not tell him the name of the suspect, but agrees to supply all the information he can.
As usual identities are concealed and connections hidden. Just like the reader, Hastings will not solve the case. That's why the world needs Poirot.
