Whilst the Watsons are delighted with their newborn, Sherlock believes, after hearing a recorded message from Moriarty, that his supposedly dead adversary has a posthumous plan to attack him. When Lestrade calls him in to solve the mysterious death of cabinet minister David Welsborough's son, Sherlock is intrigued that a bust of ex-premier Margaret Thatcher has been broken. Further incidents follow in which busts of Thatcher are destroyed, one involving murder. Sherlock deduces that a priceless jewel was hidden in one of them to smuggle it into England, but when he lays a trap for the thief, he is amazed to learn who is also innocently involved, somebody whom he must attempt to save from a vengeful associate from a failed operation six years earlier.
—don @ minifie-1