Wikipedia page about this book: https://en.wikipedia.org/wiki/The_Big_Four_(novel)

Release date is 2023-02-23

The unexpected guest -- The man from the asylum -- We hear more about Li Chang Yen -- The importance of a leg of mutton -- Disappearance of a scientist -- The woman on the stairs -- The radium thieves -- In the house of the enemy -- The yellow jasmine mystery -- We investigate at Croftlands -- A chess problem -- The baited trap -- The mouse walks in -- The peroxide blonde -- The terrible catastrophe -- The dying Chinaman -- Number Four wins a trick -- In the Felsenlabyrynth.

Greg Weeks, Mary Meehan and the Online Distributed Proofreading Team at http://www.pgdp.net

"The Big Four" by Agatha Christie is a detective novel published in 1927. When a dying stranger staggers into Hercule Poirot's bedroom and whispers about an international crime cartel, the famous detective and his friend Hastings find themselves pursuing a shadowy organization led by four powerful masterminds. Their investigation takes them across countries as they uncover kidnappings, mysterious murders, and a deadly new weapon, all orchestrated by criminals who seem always one step ahead. (This is an automatically generated summary.)

Originally published: United States: Dell Publishing Co., Inc., 1927