Charles Winlett was a geologist employed by the World Ecology Bureau. He and several of his colleagues were working at an antarctic research station when he and Derek Moberly founds a mysterious plantlike pod in a layer of ice Winlett was excavating. The two took it inside and turned it over to botanist John Stephenson. When Sir Colin Thackeray radioed the group warning them to be wary of the pod, on the advice of the Doctor, Stephenson chose to ignore the warning and let the pod thaw and possibly germinate. Winlett and Moberly urged caution but ultimately went along with Stephenson's plans, but took turns guarding the thawing pod just to be sure.
When it was Winlett's turn to watch the pod, he fell asleep at his desk, and the thawed pod sprouted a vine which stung the geologist's arm. Winlett immediately fell terribly ill and began slowly mutating into a Krynoid. When the Doctor arrived with Sarah Jane Smith, he attempted to forestall the transformation by advising zoologist Moberly to amputate the site of the original infection, Winlett's arm. Before he could, however, Winlett broke free.
He strangled Moberly to death and escaped into the antarctic wastes, where his transformation into a Krynoid continued unabated. Eventually, seeking warmth and food, he returned to the base, where he went on a rampage, endangering everyone. He killed Stephenson before the Doctor was able to shut him inside the facility's power shed. Not long afterward, Scorby's bomb blew up the entire base, killing the transformed Winlett.