With his career still in its formative years, we learn many things about how Poirot came to exercise those famous 'grey cells' so well.

The Affair at the Victory Ball [Hercule Poirot 05]

The Adventure of the Clapham Cook [Hercule Poirot 10]

The Cornish Mystery [Hercule Poirot 11]

The Adventure of Johnnie Waverly [Hercule Poirot 21]

The Double Clue [Hercule Poirot 20]

The King of Clubs [Hercule Poirot 18]

The LeMesurier Inheritance [Hercule Poirot 04]

The Lost Mine [Hercule Poirot 23]

The Plymouth Express [Hercule Poirot 07]

The Chocolate Box [Hercule Poirot 01]

The Submarine Plans [Hercule Poirot 09]

The Third-Floor Flat [Hercule Poirot 32]

Double Sin [Hercule Poirot 16]

The Market Basing Mystery [Hercule Poirot 17]

Wasps’ Nest [Hercule Poirot 34]

The Veiled Lady [Hercule Poirot 25]

Problem at Sea [Hercule Poirot 47]

How Does Your Garden Grow? [Hercule Poirot 44]