This is book 39 of the "Spenser" series.

This note contains spoilers for the book.

A nasty person who happens to be a big movie star (nicknamed "Jumbo") killed, or was present at the death of and messed with the scene, or just possibly was unfortunately in the neighborhood of a natural death (of an young girl).

Spenser is brought in to investigate by Captain Quirk (unofficially; he's afraid Jumbo may be getting railroaded, but political pressure is extreme) and Jumbo's defense lawyer (an old acquaintance).

Along the way, he meets and befriends Zebulon Sixkill, who was Jumbo's bodyguard. Z is more than tough enough, but turns out not to be any good at fighting, and Spenser eventually starts teaching him. And eventually does get useful information out of him, after really winning his trust.

This is somewhat less perfuntory than some of the Spenser novels I have read.