Companion (Doctor Who) "Face the Raven", but in a subsequent episode ("Hell Bent") her time stream is frozen at the moment of death by the Time Lords so that they can interrogate her about the Hybrid; the Doctor takes advantage of this to save her life, but she remains technically neither alive nor dead, does not age or have a pulse. After her departure as a companion of the Twelfth Doctor, she teams with the immortal Ashildr and travels in a stolen TARDIS. Other companions died in alternate timelines or alternate lives. "Brigade Leader" Alistair Lethbridge-Stewart, "Section Leader" Liz Shaw, and "Platoon Leader"
Companion (Doctor Who) a harder time recovering when a companion leaves him, especially when they do so under tragic circumstances and if the Doctor develops a strong emotional tie beyond friendship. After losing Donna Noble, the Tenth Doctor refused to travel with a companion until after his regeneration, unable to cope with them leaving anymore. Later, the loss of Amy and Rory Williams – his parents-in-law by way of his marriage to River Song – drives the Eleventh Doctor into a deep depression, and he retreats to Victorian London where he refuses to get involved in the world's affairs anymore. Additionally, "Let's Kill