Running with the Train — Kathryn Meyer Griffith

Sarah has been lonely most of her life. She's been searching for a love that she's begun to believe will never come. Her family and friends at home depend on her, need her…but they can't give her what she really wants. True, eternal love. Like the wolves have.
So as a solitary traveler, desperate to try something new and get away, she goes on an adventure of a lifetime to the Grand Canyon; rides the train from Williams to the South Rim and sees these huge wolves running alongside. Sees them in the evening twilight scurrying unbelievably below on the Canyon's ledges among the trees. She's told there are no wolves any longer in the region but she hears their haunting cries. No one else sees them and no one else hears them. Just her.
Have her senses left her; her loneliness made her crazy?
For there are wolves…unearthly prowling creatures that follow and achingly call to her…and in the end she must decide what she will do when she finally comes face to face with one.