The Doctor is recalled by UNIT to help investigate Cheng-Tiek's murder but is unaware that Chin-Lee is under the control of the Master.
Quest roles:
Richard Franklin(Mike Yates), Nicholas Courtney(Brig. Lethbridge-Stewart), John Levene(RSM Benton), Dave Carter(Sergeant Duffy), Roger Delgado(The Master), Pik-Sen Lim(Captain Chin Lee), Raymond Westwell(Prison Governor), Michael Sheard(Mergrave), Roy Purcell(President of the Council), Martin Gordon(Prison Officer), Neil McCarthy(Thawn), Eric Mason(C.P.O. Smedley), William Marlowe(Lester), Kristopher Kum(Fu Peng), Tommy Duggan(Senator Alcott), Bill Matthews(Prison Officer), Hayden Jones(Lenny Vosper), Fernanda Marlowe(Corporal Bell), Barry Wade(Prison Officer)