“River Sisters, the Strangers” completes the “River Sisters” trilogy. Great-granddaughter of Nancy Hilderbrand, Eliza McNeal, with her husband and former river boat pilot, Josh, are settled in their city home, enjoying the blessings and challenges of rearing teenaged children-Nancy Jewel, namesake of her foremother Hilderbrand, and John Henry, better known as “Hank,” named in remembrance