The Menoptra attack the Carsinome and the Doctor comes face-to-face with the Animus.
Barbara and the Menoptra hide in temple. The Doctor and Vicki flee the Carsinome.
Ian and Vrestin fall into caverns beneath the surface of Vortis and encounter the Optera.
The alien intelligence, the Animus, coerces the Doctor into tracking down the Menoptra.
Rescued by the Menoptra, Barbara is then captured by the ant-like Zarbi.
The TARDIS is pulled down to the barren world of Vortis.