Charlie Williamson is a life-long jock who's butch enough to cause plenty of raised eyebrows in gym locker rooms. Since flaming out of college on a wave of drugs, alcohol, and depression, she's worked the same easy, low-stress job at RRiotWear-a women's fitness clothing startup in Chicago. Then with a promotion on the horizon, Charlie's boss ropes her into leading a beginner's marathon group in the RRiotWear facilities. Elizabeth McIntyre runs a boutique tech company. Since graduating from MIT, she's made herself into the face of women in technology. She has a beautiful apartment she never sees, a string of ex-girlfriends, and a propensity for panic attacks. When her doctor confirms what her best friend has been saying for years-that Elizabeth needs to slow down and make some radical life changes-she signs up for RRiotWear's marathon program. Despite everything that points to a not-so-perfect fit, the attraction between Charlie and Elizabeth grows week after week, and mile after mile. But with secrets lingering between them, they might find their relationship stumbles before it can even get to the starting line.