Be Careful What You Wish For opens with Harry Clifton and his wife Emma rushing to hospital to learn the fate of their son Sebastian, who has been involved in a fatal car accident. But who died, Sebastian or his best friend Bruno? When Ross Buchanan is forced to resign as chairman of the Barrington Shipping Company, Emma Clifton wants to replace him. But Don Pedro Martinez intends to install his puppet, the egregious Major Alex Fisher, in order to destroy the Barrington family firm just as the company plans to build its new luxury liner, the MV Buckingham. Back in London, Harry and Emma's adopted daughter wins a scholarship to the Slade Academy of Art where she falls in love with a fellow student, Clive Bingham, who asks her to marry him. Both families are delighted until Priscilla Bingham, Jessica's future mother-in-law, has a visit from an old friend, Lady Virginia Fenwick, who drops her particular brand of poison into the wedding chalice.