This is book 3 of the "Modesty Blaise" series.

This note contains spoilers for the book.

This one's definitely supernatural; Lucifer predicts deaths by psychometry, and is two seconds ahead of Modesty in a fight. And Willie's ears tingle.

There's a nice scene where Stephen Collier meets Willie when Willie comes into the apartment (Collier having not answered the bell). And in a little while they go to rescue Vaubois from not one but two attempts to murder him.

Turns out the baddies are using Lucifer's powers for a rather clever scheme. They pick people very likely to die according to Lucifer, and likely not to pay protection money according to a psychiatrist, and other people likely to pay protection money, and publish them as a list, giving each instructions on how much to pay and how to do so. Then the ones that don't pay and don't die naturally are murdered (a small number). The number of natural deaths makes the whole thing very hard to analyze.