“But the one thing I know for sure, this is the one life you have and you have to make it work.” Some novels make the meat and bones of their plot out of one shining secret; Tea by the Sea feasts on a profusion of furtive mysteries. In Jamaica-born Donna Hemans’s second novel, winner of a Lignum Vitae Una Marson Award for Adult Literature, the search for answers salts a trail through Plum Valentine’s life.