This book introduces Sid Halley who, if memory serves, is the only protagonist that Dick Francis ever used more than once. Halley was a very successful jockey until he fell from a horse which trampled his left hand, abruptly ending his career. He accepts a job with a detective agency that has a racing division, but he spends a couple of years simply hanging around the office without being given any meaningful assignments. But he's willing to go with the flow, or the not-flow, as the case may be, because he's still trying to figure out what his future is going to be now that the one thing he really loved has been taken from him.
Things take a turn for the worse when one of the detectives in the office asks Halley to assist him in a minor sting and Halley winds up being shot. Now he has a crippled hand and a ventilated stomach, which will take some time to heal. His wealthy father-in-law asks Sid to visit over a weekend and Halley agrees to do so. (Sid's wife has left him, which is not at all uncommon for a protagonist in a Dick Francis novel, but he's still on good terms with her father.)
The father-in-law has an ulterior motive, which Halley soon discovers. The other weekend guests are a particularly obnoxious man and his equally disagreeable wife who enjoys being knocked about while having sex. Without telling Halley what he's up to, the father-in-law cleverly manipulates things so that Halley will wind up investigating the disagreeable guest.
The bad guy is apparently involved in a nasty scheme to sabotage a race course so that he can gain a controlling interest and turn the place into a housing development. Well, of course, we can't allow something that horrifying to happen, but once Halley is on the job, a lot of other very horrifying things will happen--most all of them to him.
Dick Francis is a very dependable author who almost always tells an interesting tale that moves swiftly along, and this book is certainly no exception. Although the protagonists do vary in nearly every book, there is a certain formula at work in these novels, and the principal characters are almost always of a type. That's certainly not a problem, and any fan of the series will want to look for this entry.