The Secret Adversary
Like its predecessor, "The Mysterious Affair at Styles", "The Secret Adversary" was first published as an unillustrated serialisation in "The Times" weekly edition (aka "The Weekly Times") as a complete and unabridged text in seventeen instalments from 12 August (Issue 2328) to 2 December 1921 (Issue 2343). Christie was paid £50 for the serialisation rights (£1,545 in 2003 currency).