When the Brigadier and Jo are called in to look into a breakthrough in the field of portable communication, the Doctor has to stay behind with communications problems of his own – a strange signal coming through the TARDIS console that’s burned out its circuits.

When Benton approaches the Doctor with an odd story about an old friend, the Time Lord realises his troubles and the Brigadier’s investigations may be connected, and hot-foots it in pursuit.

Soon they discover that terrifying sounds are walking in the woods of the English countryside... but what lurks behind those sounds may be even more dangerous...