- He's born in the 51st Century in the Boeshane Peninsula. We don't know his real name. He loses his brother Grey to alien invaders when he lets go of Grey's hand, allowing him to be captured and tortured. He becomes the first resident of Boeshane to qualify for the Time Agency, and thus becomes a poster-boy for the place, known as the "Face of Boe"...
- As a Time Agent, he's partnered with "Captain John Hart" (under a different name). They're trapped in a two-week time loop for five years, during which they have a relationship ("John" is the wife). "Jack" is also Rear of the Year 5094. He's sentenced to death on one occasion but ends up in bed with both his executioners. He eventually leaves the Time Agency upon waking up and discovering that they have erased two years' worth of his memories (this has never been followed up on).
- He becomes a con-man to survive, and while executing "the perfect self-cleaning con" during the London Blitz of 1941, meets the ninth Doctor and Rose Tyler in Doctor Who Series 1. He has by now adopted the alias "Captain Jack Harkness" from a dead American GI. He joins the TARDIS and travels with the Doctor and Rose for a while, visiting 21st Century Cardiff along the way while the Doctor refuels the TARDIS from the Space/Time Rift. He goes into battle against the Daleks on the Gamestation in 200,100, where he is exterminated and resurrected by Rose using energy from the heart of the TARDIS. Unbeknownst to him, and Rose, he is now immortal. The Doctor is frightened by the breach in the laws of physics that Jack now represents, and runs away from him, abandoning him on the Gamestation.
- Jack still has his old Time Agent's Vortex Manipulator, and uses it in an attempt to travel back to 21st Century Cardiff, where he knows the Doctor will visit at some point to refuel the TARDIS again, but he overshoots and arrives in 1869, where the VM shorts out, leaving him stranded. He eventually discovers his immortality when he is shot and killed during a bar fight on Ellis Island and wakes up. In the late 1800s, having not aged since his original resurrection and having been killed several times, he comes to the attention of Queen Victoria's Torchwood Institute, who draft him in as a freelance agent. He initially declines, but accepts when a mysterious tarot-reading little girl informs him that he will one day meet the Doctor again, but that "the century will turn twice" before that day. Needing something to do and a means of living in the meantime, he joins Torchwood.
- Throughout the 20th Century, Jack operates as a freelance Torchwood agent before joining full-time. This is when most of the flashbacks in Torchwood take place. He encounters the Fairies and the Night Travellers, marries at least once, lives through WWII again, during which he falls in love with Estelle Cole, is complicit in the sale of 12 children to the 456 in 1965, and fathers Alice Carter with fellow TW agent Lucia Moretti. All the while he waits to encounter a version of the Doctor whose timeline will coincide with his.
- He inherits Torchwood 3 in Cardiff at the stroke of midnight on New Year's Day 2000, when leader Alex Hopkins kills himself and the rest of the team. Jack then sets about recruiting a new team - Susie Costello, Toshiko Sato, Owen Harper and Ianto Jones. Gwen Cooper stumbles upon the organisation and replaces traitor Susie in the first episode of Torchwood. The first series/season takes place, leading into Jack's reappearance in Doctor Who in Series 3, when the TARDIS finally materialises above the Torchwood Hub for a pit stop.
- Jack briefly rejoins the Doctor after 150 years and meets Martha Jones, and travels to Malcassairo where the TARDIS crew encounters the Master. The events of the Series 3 finale take place, and Jack is part of the Year That Never Was, during which time he is chained up on the Valiant and realises that his place is with his team. When the year is "undone", he leaves the Doctor by his own choice and returns to Torchwood.
- The events of Torchwood Series 2 take place, during which Jack's brother Grey returns seeking revenge, Jack encounters Captain John Hart once again, Owen and Toshiko are killed in action, and Jack and Ianto fall in love. Jack is taken back in time by Grey to Cardiff in 27AD, and buried alive. He is found and awakened in the late 1800s (having presumably been unconscious during the previous thousand years) by the Victorian Torchwood. Jack convinces them to place him in cryogenic suspension so that he can be woken up in 2007 to stop Grey. So, at various points throughout the 20th Century, there are several Jacks co-existing - the immortal Jack living through the century working for Torchwood, the younger Jack working his con in 1941 (and probably various others), and the one secretly frozen in the Hub for 100 years.
-Torchwood: Children of Earth. The 456 return. The 100+ year-old Hub is destroyed by the British Government. Ianto is killed. Torchwood disbands and Jack leaves Earth after being forced to sacrifice his grandson Steven (son of Alice) to defeat the aliens. We next see Jack briefly in Doctor Who's The End of Time Part 2, drowning his sorrows in a space bar, where the Doctor pimps him out to Alonzo Frame.
- Torchwood: Miracle Day. Jack will return to Earth...
Just realised I missed out Torchwood's appearance in Doctor Who's Series 4 finale, between Torchwood's S2 and CoE, when Jack meets the Doctor, Rose, Martha and the Daleks again and helps save the Earth.
