The Tenth Doctor discovers a museum dedicated to his lives and has to remember events from his previous incarnations in order to restore his fading memories.
It is revealed that it is the TARDIS Matrix that has taken the form of Martha throughout the story; the Matrix proceeds to take on the forms of Harry Sullivan, Leela, Mel, Steven Taylor, Sarah Jane Smith, Adric, Nyssa, Kamelion, and, finally, Susan Foreman. Although he isn't impersonated, Sabalom Glitz is also mentioned, creating confusion as to whether Glitz has travelled with Doctor or not.
Last Great Time War
During the flashback featuring the Eighth Doctor, he is shown being held prisoner on a planet at some point during the Last Great Time War. He manages to escape and steal the Great Key. The Doctor intends to use this key to create a device similar to a De-mat Gun that will seal the Medusa Cascade and somehow end the war.
The Tenth Doctor refers to Romana II's involvement in the war, and claims that it didn't turn out well for her.
The Tenth Doctor states that he succeeded in ending the Last Great Time War using the Great Key. It is implied that this key was used to create the time lock, which closed off the war from the rest of the universe and repelled any time travellers from entering by normal means.
Species
The First Doctor mentions that the Egyptian gods Sutekh and Horus were aliens.
The Controller of the museum unleashes a number of 'relics' to attack the Doctor and Martha. These include: Clockwork Droids, members of the Eight Legs, an Auton, and a Voc Robot.
Each of the previous Doctors had a display dedicated to their particular incarnation. The display consisted of their outfit, plus an item associated with them. These items include:
The First Doctor was given his walking stick by Kublai Khan. The Tenth Doctor at first claims he obtained it in an unchronicled adventure involving Oscar Wilde and "midget assassins", but he later admits it was a ruse to trick "Martha."
The Forgotten was a comic book mini-series produced by the American company IDW Publishing in the fall of 2008, following on from its initial Doctor Who title Agent Provocateur.
This was the first officially sanctioned spin-off to feature all ten (at the time) of the Doctor's incarnations.
It was collected and reprinted as the graphic novel The Forgotten in April 2009.
Due to a printing error, the dialogue balloons on Page 1 of Issue 6 were left blank. The absence of the dialogue had caused confusion over whether the villain was meant to be the Meta-Crisis Tenth Doctor or the Valeyard, since most references to it were on this page (although the Doctor refers to the villain as the Valeyard on a later page). Tony Lee posted the missing dialogue on IDW's web forum [1], and the dialogue was fixed in the trade paperback release.
The fact the villain takes the form of the Meta-Crisis Doctor, and refers to himself as the Valeyard, added credence to the theory that the Meta-Crisis Tenth Doctor could be destined to become the Valeyard. The Doctor, however, laughs at the idea. Until such a time as a connection is actually made, the fact the villain chooses "the Valeyard" as his alias means that, regardless of his appearance, the villain being impersonated here is indeed the Valeyard.
This story contains several plot points reminiscent of the novel The Eight Doctors.
The Tenth Doctor loses his memory, like the Eighth Doctor.
The Doctor revisits, after a fashion, the events of his past adventures.
The Doctor has an encounter with his previous incarnations, though in this case it is mental projections of them rather than the genuine articles.
Continuity
During the First Doctor's vignette, presented in monochrome as a reference to the early seasons of the series being aired as such, the Doctor hopes the TARDIS team doesn't end up in an Aztec temple. The Doctor and his companions did this in TV: The Aztecs.
The mysterious man at the controls in Issue 1 sports a beard similar to that sported by the Roger Delgado and Anthony Ainley incarnations of the Master. The Doctor himself comments on the similarity when he tries to use one of the Master's devices on him. Later, the character's identity is revealed to be an insectoid creature impersonating the Meta-Crisis Tenth Doctor.
During the Eighth Doctor's flashback, it is suggested that his statement of being "half-human" in TV: Doctor Who was a ruse.
The final issue establishes that the events of The Forgotten occur immediately following the final scene of TV: Journey's End.
In the Ninth Doctor tale, Captain Jack Harkness is mentioned. A soldier mentions a Captain Harkness being shot in the head and surviving with "not a scratch to be seen", suggesting this is the version of Jack who is already immortal. According to Jack's backstory in TV: Small Worlds, Fragments, and Immortal Sins, Jack left Torchwood Three to fight in both World Wars. At this point in their timeline, the Doctor and Rose have not met Jack yet. (TV: The Empty Child)
The Doctor tells the fake Martha that he was all alone when his eighth incarnation died. This was shown in [TV]]: The Night of the Doctor, where he was indeed alone and companionless when dying, losing his life after travelling by himself, avoiding the Time War. After dying in a spaceship crash, the Doctor was briefly resurrected by the Sisterhood of Karn, and was given the chance to choose the nature of his next incarnation before he truly perished. Opting to become a warrior, he demanded to be alone before he began to regenerate.
For the purposes of this list, an "Auton story" is one in which one living, authentic Auton plays a part within the confines of the story, outside of flashbacks to previous stories and cliffhangers that lead into the following story. For this reason, stories such as Love & Monsters are absent due to the Autons' only contribution being references to past Auton stories.
For the purposes of this list, a "Homo Reptilian story" is one in which one living, authentic Silurian or Sea Devil plays a part within the confines of the story, outside of flashbacks to previous stories and cliffhangers that lead into the following story. Stories like Frontier in Space, The Pandorica Opens and The Wedding of River Song are also not included due to Homo Reptilians' cameos being of little consequence to the plot of the story. Stories featuring MadamVastra of the Paternoster Gang are only included on the Paternoster Gang story template.