'Drift', written by Simon A. Forward, features the Fourth Doctor and Leela.
Back Cover Blurb
White: the perfect camouflage for ghosts.
White consumes the New Hampshire ladnscape, and troops move in on a survivalist cult following a spate of unnuaturally severe blizzards. The Special Forces group, White Shadow, is searching for the missing fragments of a US Air Force jet, crashed while engaged in top-secret test flights over the region.
The Doctor and Leela have arrived at quite literally the wrong time. Thanksgiving is approaching - traditionally a holiday all about home and family. But htis year, all that is lost.
Lost: like the local community, in the grip of something far more sinister than a harsh winter. Like you Amber Mailloux, victim of a broken home that won't even settle in one place. Even White Shadow is lost, out of its depth and up against an enemy not even the Doctor can find in this world of white.
An Enemy that promises the bleakest of midwinters for the people of New Hampshire, and befoere springtime, the end of life on Earth...