Meet June Parker. She works for L.A. Rideshare, a pro-carpooling agency, adores her rent-stabilized apartment in Santa Monica, and struggles with losing a few pesky pounds. June's life is about to change. After a turn of events involving Weight Watchers, a taco soup recipe, and a car accident in which her passenger, Marissa, dies, June finds herself in possession of a list Marissa has written: "20 things to do by my 25th birthday." Even though they barely knew each other, June is compelled--by both guilt and a desire to set things right--to finish the list for Marissa. The tasks before her range from inspiring (run a 5k, watch a sunrise) to daring (go braless) to near impossible (change someone's life). As fun-filled as the list must have been for Marissa, it's not going to be easy for June, who's spent a lifetime falling short. But challenging though it will be, June is determined to make Marissa's dreams come to, and as she races to achieve each goal before the deadline, she learns more about her own dreams than she ever bargained for.