New York real estate broker Miriam Lewis takes off for a brief getaway to a remote inn on the rugged cliffs of Cornwall. Rest and romance with her boyfriend seem like the perfect cure for a life that appears to be going nowhere, and too fast.
Entering Cornwall, Miriam crosses the River Tamar and glimpses a luminous girl floating in the river. A memory from long, long ago begins to unfold in Miriam’s thoughts—something about a promise she made to perform a selfless act of courage. Could it be true? Could she ever rise to such heroism or is it just a hallucination?
While at the inn, Miriam experiences a series of flashbacks from a life she lived in an ancient land called Ruberah. These startling images convince Miriam that she did write the promise and that she must keep it. But to do so, Miriam will have to let go of everything in her life and place her trust in a guide—the river girl—the wise and eternal spirit of the River Tamar.