Captain Jack Harkness was the alias adopted by a Time Agent and con man from the 51st century who became an associate and occasional companion of the Doctor. He was made immortal when killed by a Dalek and revived by Rose Tyler using the energy known as the “Heart” of the TARDIS (absorbing its full power), and stranded on Earth from the mid-19th to the early 21st century. During much of that time, he worked for Torchwood Three until its destruction in 2009. He left Earth in 2010 and did some soul-searching. However, he returned to Earth in 2011 when Miracle Day spread across the world, founded a new Torchwood team and returned mortality to humanity.