What would you do if an old friend needed you, but it meant turning your new life upside down? Pen, Will, and Cat met during the first week of their first year of college and struck up a remarkable friendship, one that sustained them and shaped them for years - until it ended abruptly, and they went their separate ways. Now, six years later, Pen is the single mother of a five-year-old girl, living with her older brother in Philadelphia and trying to make peace with the sudden death of her father. Even though she feels deserted by Will and Cat, she has never stopped wanting them back in her life, so when she receives an email from a desperate-sounding Cat asking her to meet her at their upcoming college reunion, Pen goes. What happens there sends past and present colliding and sends Pen and her friends on a journey across the world, a journey that will change everything.