Queen of Swords (Wilderness #5) by Sara Donati

It is the late summer of 1814, and Hannah Bonner and her half brother Luke have spent more than a year searching the islands of the Caribbean for Luke's wife and the man who abducted her. But Jennet's rescue, so long in coming, is not the resolution they'd hoped for. In the spring she had given birth to Luke's son, and in the summer Jennet had found herself compelled to surrender the infant to a stranger in the hope of keeping him safe.