Hovering just above Alaska in 1964, the TARDIS picks up some strange energy emissions of a type the Doctor and Nyssa cannot make head nor tail of. Before they can try, they are forced to dematerialise to avoid a collision with a light aircraft. But the TARDIS is apparently following a scent and takes them to the same place in time, but thirty years later.

There they encounter a new kind of habitat, occupied by the obssesive Englishman Brett, Monica his interior designer and Tulung, the half-Inuit, brought up in America. Something in the snowy wastes of Alaska doesn't seem to want this new intrusion, and before long it appears as if the local spirits, revered by the Inuits, scorned by Brett, may be making some drastic attempts to erase Brett's structure and the secrets it contains from the face of the planet.

If the Doctor can discover exactly whst Brett has been doing, he may find a way to halt the assault, but Nyssa seems to be "in tune" with the spirits - although she does't entirely like what she sees...