Release Message:  The Doctor (Peter Davison)'s TARDIS is stolen, and tracking it down reveals the existence of an alien named Kalid controlling events in the past.

Description:  The Doctor's TARDIS is stolen, and tracking it down reveals the existence of an alien named Kalid controlling events in the past. While the Doctor challenges Kalid's motives for being there, Tegan and Nyssa discover the source of Kalid's power - an even greater threat for the Doctor.