The Clue of the Red Tresses

Stephen Longstreet has been charged with a task: find out who's been borrowing his Uncle Anthony's greatest invention, a time machine, without permission. He never expects the miscreant to be a lovely, red-haired woman, or that in apprehending her one dark night he'll fall into the contraption and travel through time with her. But once he's met Bridgetta Maguire and discovered her powerful mission, his heart refuses to let him turn away.
Bridgetta isn't sure how or why the time.