This special sees the return of the Cybermen (of the design of the parallel universe's Cybus Industries Cybermen), following their previous appearance in the two-part finale of series two in 2006, "Army of Ghosts"/"Doomsday". Having fallen back in time to Victorian London, the Cybermen create a huge "Cyber-King" with child labour and the help of Miss Hartigan (Dervla Kirwan). Meanwhile Jackson Lake (David Morrissey) has accidentally absorbed the Doctor's memories and thinks himself to be the Doctor.