After the fall of Gallifrey, and before he found Rose, the Doctor had a different companion. A younger one. Meet Ella, the Doctor's youngest companion.
Fresh from the Time War, the Doctor lands in Dublin where he meets a lonely young girl named Ella Lawrence. A string of disappearances leads to a dangerous mystery for the Doctor to solve. Add in a ruthless alien leader, a rebellious teenager, and the machine that could change the world forever, and you've got quite a story.
(The Doctor, The TARDIS and his universe all belong to BBC. Ella and all other characters are mine)