This book, from 1947, is the last full-length Saint novel written entirely by Charteris (i.e. not ghost-written with his approval); and it features its hero still in his reformed wartime rôle of rather eccentric G-man, on the trail of drug smugglers in New York.
Charteris's story-telling and character-drawing abilities, with the characteristic flashes of humour, never entirely desert him. But compared with the prewar books, this is dull stuff.
There is one point of especial interest, nonetheless. The Saint says to the heroine:
"[T]his thing goes too far over the world, into too many countries and too many jurisdictions. Only an organisation that's just as international can cope with it. There is such a thing, and I'm part of it. That's all I'm allowed to say."
But on the last page the organisation is clearly identified as UNCLE, over a decade before this supposedly fictional organisation was supposedly created for the TV series.
P.S. For a list of all Charteris's Saint books (in two sections, because of length limitations) see my Listmanias.