Bill Strutton

Affected by a strange force, the TARDIS is dragged down to the desolate planet of Vortis. The Doctor, Ian and Vicki are captured by the Zarbi – huge ant-like creatures controlled by the parasitic alien Animus. Meanwhile, Barbara runs into a group of Menoptra, butterfly-like creatures that have been driven from their home planet by the Animus, and plan to return with an invasion force. But the Zarbi know their plans and are waiting for the Menoptra...

In this vintage six-part serial, first shown on BBC TV in February and March 1965, a strange magnetic force pulls the TARDIS down to the craterous surface of Vortis. The Doctor and his friends learn that the planet has been invaded, and the parasitic Animus is slowly enveloping it in a web-like domain. The giant ant-like Zarbi are under its control, whilst the butterfly-like Menoptra are battling to reclaim their planet.