The Power of Six continues the story of I Am Number Four, with the Mogadorians chasing Numbers Four, Six and Seven across Planet Earth! Number Four, whose Earth name is John Smith, has just lost his Cepan, or guardian, and is trying to discover the secrets of his Loric chest, which has travelled with him from his home planet of Lorien. The Mogadorians, an alien race who have already attacked and destroyed Lorien, are bent on finding and destroying the remaining Loriens, who are hiding on Earth. They can only kill them in order of their numbers, so it is important that Number Four stays safe, as they have already killed numbers One, Two and Three. The friends have to find the other numbers, who are still in hiding, and try to fight the Mogadorians together. This book is fantastic - I can't wait for the next one!