An American socialite commissions ex-jockey Jonah Dereham to buy a steeplechaser for a "special" friend of hers. At the Ascot sales, Jonah purchases a modestly priced horse he thinks will meet her specifications, only to find that someone else want the same horse - and is willing to kill to get it. Why has this undistinguished steeplechaser suddenly become so valuable? Is there something in its bloodlines that even the experts don't know about?