Jack and Teraise begin to fear the worst, while Cher gets fed up with Sita and teams up with Nat.
This week's episodes written by Brian B Thompson
(Next episode Thursday) (Repeat)
Followed by Rewind: 1974: Giant Pandas
Ben Ridgeway tells 11-year-old William Brambell's story of Chia-Chia and Ching-Ching arriving at London Zoo from China.
(Repeated tomorrow morning on BBC2)