The Doctor and Donna are walking into a trap. An enemy known as Leon lurks in the darkness, scheming and planning in secret, but he is protected by his children. His children are no ordinary children, they have no mother, but were born to different elements, fire, water, wind, earth, light and dark. Leon treats his children like part of a collection, but his collection is not complete. However, Leon knows how to remedy that. Two more pieces of the puzzle are needed until Leon can have his seventh child, the child of Time, and for that he would need the Doctor and the TARDIS.