Sanity and Tallulah are going on a field trip—to a real live planet! Some of their classmates are nervous (none of them have been on a planet before, and they've heard terrible things), but Tallulah is beside herself with excitement. Sanity would be more excited if her grumpy older sister, Prudence, wasn't coming along to supervise the trip. Things get off to a rocky start (asteroid-y start, to be specific) and Sanity and Tallulah find themselves separated from their school group, pursued by a pirate, and stranded on a planet that's about to explode, with nothing but the wreckage of a crashed space shuttle and the contents of Tallulah's overloaded backpack to work with. These best friends will have to stretch their problem-solving skills to the limit in order to get everyone home safe, and it's going to take their whole class—plus an accountant, a math hermit, a group of mysterious beekeepers, and even the murderous pirate—to make it happen.