'Somewhere, somehow we are being slowly dragged down...'

When the Doctor and his friends stray from their astral plane and the TARDIS materialises in eerie alien surroundings, a mysterious force prevents them from leaving. Is it a natural phenomenon or some malevolent intelligence? Uncanny occurences are followed by encounters with the deadly Zarbi and their unknown leader, to whom the travellers fall prey. With their allies, the Menoptra, the travellers must discover how to immobilise the Zarbi, save the Menoptra from massacre and rid the planet of this powerful and horrifying evil. As a growing web building begins to envelop the planet, imprisoning the travellers in its mesh, the Doctor must consult all of his wisdom to escape its hypnotic power. But what is at the centre of the web and from where does it draw its power?

Originally transmitted 13/02/65 - 20/03/65