Summer’s Distant Heart by Laura Landon

Two wary souls, one tyrannical father, and no way to avoid a deadly clash.
Amelia Halloway has lost her sister and gained an infant nephew. She knows she can keep him safe, as long as the child’s grandfather never hears of his existence. And it’s working, until Lord Atherton arrives on her doorstep—a handsome devil whose father wishes the child dead.
He says he’s there to save his nephew. But can she trust him?