Notes: Frobisher's shape-changing abilities, which had inexplicably disappeared a few issues back, suddenly return with no greater explanation.This story unusually takes place entirely in the TARDIS. As the Doctor and his companions travel deeper into the TARDIS, they go further into the ship than has ever been visually depicted before or since, in any medium. Deep at the heart of the TARDIS, they even find the TARDIS memory banks, or what are essentially the Doctor Who equivalent of Star Trek's holodeck. Significantly, this occurred prior to the proper introduction of the Holodeck in Star Trek: The Next Generation.This story also marks a debut of the "Season 23 Peri"that is, less bikinis and more business suits. This part of the story attempts to retcon recent damage done to the notion of "the state of Temporal Grace". First introduced in the story which saw the departure of Sarah Jane Smith, "The Hand of Fear", the TARDIS was said to be a place that weapons wouldn't work because it existed in a "state of Temporal Grace". Several stories in the FIfth and Sixth Doctors' eras, however, had recently flouted the notion. This story attempts to rectify that problem by suggesting that Temporal Grace only exists while the TARDIS is in flight. This of course, makes the concept rather less useful, but it does neatly explain away the post-"Hand of Fear" instances where guns have been successfully discharged inside the TARDIS.