Sea Lord by Bernard Cornwell
Johnny Rossendale has spent the last four years on the seas, away from the titled family he despises. But now he must turn his sailing cutter, the Sunflower, around and sail to Devon, where his mother lies dying.
When Johnny makes landfall, though, he finds that his return is eagerly anticipated by some very sinister foes. After an attempt on his life, he realises that someone thinks a missing painting that belongs to the family is in his hands - and, worse, they are prepared to go to any lengths to get hold of it.
But as Earl of Stowey, Johnny has eight centuries of robber-baron blood pumping through his veins. He won't let the family fortune fall into the hands of others without a fight . . .