This is book 7 of the "Modesty Blaise" series.

This note contains spoilers for the book.

An early one, perhaps the second? I never paid that much attention to order. Maybe someday I should read them all in order.

Wow, I never knew Tor published these in the 1980s! (Mine are mostly British paperbacks from Pan, and then later US hardcovers from Mysterious Press).

This one has a very clever blackmail scheme. They get information from therapists and various other sources (they kidnap Tarrant early on to get information from him), and get relatively small payments sent to a fake charity. This gives the victim cover, and even a tax deduction. This is set up through a crooked bank that Modesty knows all about.

Turns out Willy's girlfriend's sister is being blackmailed by these people, and they've just snatched Tarrant (the story at first is that he's dead) on his way to visit Modesty. Two capers in one! And the clue comes from crazy old Quinn, concussed and fading in and out on the shelf across the gorge. Modesty finally noticed that his saying "I didn't see it go over" suggests he did see the gray Peugot across the gorge.

And this one has the fight against Mr. Sexton. Fights, actually; he takes Willy and Modesty when they first come into the Chateau, but Modesty takes him later down in the cave. Tarrant gets to watch.