It's 1969 and the country is gearing up for men walking on the moon. Ten-year-old Mamie's class is given an assignment to write letters to the astronauts, and she is the only one who writes to Michael Collins, the astronaut who doesn't get to walk on the moon because he has to stay with the ship. After school ends for the year, Mamie keeps writing to Michael Collins, taking comfort in telling someone about what's going on with her family. One by one, they each leave her thinking that someone else is taking care of her - until she is all alone except for her best friend, Buster, who lives next door. As the launch nears, everyone in the country is on the edge of their seats: Will the mission be successful? For Mamie, there's even greater turmoil, and she can't help but wonder: Does no one stay with the ship anymore?