Desperation
Time was running out for Peri!
She should never have consumed that lethal potion. Now she felt unable to move for fear that any motion would only hasten its vile effects.
Leaving her here alone in this cold, bare room the Doctor had gone to find a means of opening the locked door behind which lay her only hope of salvation. But that surely had been hours ago?
Finally! The Doctor rushed into the public convenience and threw some copper coins to the desperate and now slightly malodorous girl.
"Change, my dear. And it seems not a moment too soon."