Walter Griffin has only one plan for the summer before eighth grade —- to follow the inaugural season of the Washington Nationals. His twelve short years have been steeped in baseball lore and statistics, especially a team he never saw play, the storied Washington Senators. He even claims to be named after Senators pitcher Walter Johnson. However, a few days into the season, his plans change when Elysia moves in down the street.

Despite his father’s warnings not to befriend children of political appointees (his father is an old school socialist), Walter ends up hanging out with the Kansas refugee. Elysia’s superior ability to hit a fastball might have some influence, as well as her procurement of Nationals tickets. After attending his first game with Elysia, Walter tags along to a Tarot parlor, where Madame Cassandra’s cards reveal shocking news about Elysia’s impending death. Elysia locks herself in her house out of an irrational fear of death, Walter makes it his duty to get her out. He convinces her to pursue all the things she’d like to do before she dies. What follows is a whirlwind spending spree and adventure that Walter can only compare to a baseball pennant race. But then Elysia decides she is being too selfish and must ‘accomplish something’ with the time she has left.

Walter, perhaps to young to notice before, becomes acutely aware that his parents don’t like each other very much, and he is constantly caught in the middle of their ever-increasing skirmishes. The safest route out of the war zone, he decides, is to bravely follow Elysia in her pursuit of ‘world peace’ or ‘inventing something for the ages’ or whatever she has decided she needs to do before she dies. Elysia even steals all of her father’s clothes to give away to homeless people.

As the summer passes, and the Nationals drift away from play-off contention, Elysia realizes that she hasn’t died like the cards said. She returns to Madame Cassandra and demands an explanation. Told that certain people are able to defy their fates, Elysia suddenly believes that she CAN’T be killed. Her adventures now become extremely reckless, like swimming across the Potomac River, and all Walter can do is follow and try to minimize the danger to which Elysia thinks she is impervious.

As Walter watches his parents’ relationship crumble, he sees how close he has become to Elysia. When Walter and Elysia take a secret pilgrimage to see the ocean, she becomes very ill. Walter thinks the trip made Elysia sick, but Elysia’s father confides to him that she has a terminal disease. Elysia’s father never told her because he wanted her to have a normal life. Walter is outraged by the selfishness that every adult around him seems to exhibit, and after Elysia passes away, he returns to Madame Cassandra to throw her prophecy in her face . . . only to find that the Tarot reader is just as distraught over Elysia’s death because Elysia was actually her niece.