Sabatini Rafael. The Lion's Skin

Justin Caryll was raised by his guardian, Sir Richard, knowing neither his deceased mother nor his father, the Earl of Ostermore. Ostermore and Sir Richard had been friends and suitors of the same woman, and Richard grew to hate his friend after the former won the French lady and then went back to England, abandoning her pregnant and alone. At her dying request, Richard raised her son, and Caryll was taught that one day he would be called upon to exact revenge on his father. As the book begins, Justin Caryll is an adult who journeys to England with the means to ruin his father, only he has misgivings about the whole idea. As he tries to decide what to do, he makes Ostermore's acquaintance, earns the enmity of Ostermore's son -- Viscount Rotherby -- and gets on rather well with Ostermore's ward, Hortensia Winthrop. Meanwhile, he is rightfully suspected by his enemies of being a Jacobite agent and he realizes that there is very little to hate in his mild-mannered father. In the end, Rotherby and a few others think they have what they need to get Caryll out of the way, but too late they learn the meaning of that phrase from Henry V that inspired the title, and which Caryll actually quotes: "the man that once did sell the lion's skin/while the beast liv'd, was killed with hunting him."