The Chelsea Park Zoo is a small zoo, and a slightly run down one at that. But to twins Andrew and Allison, it's their favorite place in the world. To the animals who live there, it's their home. And to the kindly, gentle zookeeper, Morgan, it's his life. So when the city announces the zoo will be shut down and the animals shipped to zoos all over the country, the twins -- and the animals -- spring into action to save Morgan's Zoo. But closing the zoo isn't the only danger afoot. The animals soon discover they have a chance to do more than save their home -- they have a chance to become heroes.