**A USA TODAY bestseller** A riveting narrative of love and loss, grief and joy, as one woman embarks on a quest for a record on the Pacific Crest Trail. When Emily Halnon lost her beloved mother to a rare uterine cancer at just sixty-six years old, she wanted to do something monumental to honor the person her mother had been: adventurous, courageous, inspiring. Emily’s mom had taken up running in her late forties; she ran her first marathon at fifty. She learned to swim at sixty so she could do triathlons, and she lived through a grim diagnosis with extraordinary joy and strength, still going for long bike rides and walks up until the final weeks before her death. She even went skydiving to celebrate her sixtieth birthday. It was going to take something special to pay tribute to such a remarkable, lifeloving spirit. Emily, already an accomplished ultrarunner (inspired to initially start running by her mother), decided to try to break the record for the Fastest Known Time by a woman