When Margot Blumenthal removes a bright blue slug alien attached to Mateo Flores s back, the school play costars know it s definitely not going to be a regular day at West Cove Middle School. They reluctantly team up and soon discover that the mayor and countless other adults, including Mateo s dad, are infected which means that West Cove, and possibly all of Earth, is in danger. What will they (and their new scientist friend) do?