Misplacements was what Alistair Gordon Lethbridge-Stewart's eccentric scientific advisor referred to phenomena who "haunted" the HQ of Lethbridge-Stewart's organisation, and which resembled ghosts.
Misplacements were a few seconds in the lives of individuals who had died in this place, separated from their normal time-stream, which replayed themselves over and over at unpredictable intervals. The two "ghosts" of the HQ were the Solitary Egyptian and the Screaming Soldier. There was no way of preventing the misplacements from continuing to appear indefinitely; the Brigadier ended up seeing the bright side of having these apparitions in the HQ, as they'd harmlessly test the mettle of new recruits when it came to living side by side with inexplicable phenomena. (AUDIO: Memories of Tomorrow)