Therefore, its known narrative elements are not a part of the Doctor Who universe as we, on this Wiki, choose to define it. It may have been the basis for a similar story in another medium, however — and that story may indeed be valid.
The Laird of McCrimmon was an unmade Doctor Who serial written by Mervyn Haisman and Henry Lincoln. It would have aired during Season 6 and would have featured the Second Doctor, Jamie McCrimmon and Victoria Waterfield, who in actuality departed during the previous season. Had the serial been made, it would presumably have featured Zoe Heriot instead. A candidate for Frazer Hines' departure story, it was abandoned in August 1968 due to a dispute which arose between the writers and the BBC regarding the copyright of the Quarks, who made their first and only appearance in televised Doctor Who in The Dominators, notwithstanding a brief cameo in The War Games.
The story would have involved a possessed Jamie piloting the TARDIS to 1746 Scotland and his ancestral home, Castle McCrimmon, at some point after the Battle of Culloden, the aftermath of which was depicted in The Highlanders. There, he finds the current laird, Sir James McCrimmon, on his deathbed. Yeti appear and surround the castle where the local villagers fall under the influence of the Great Intelligence. The only person who seems to be immune is a girl named Fiona, with whom Jamie falls in love. The Great Intelligence wants to inhabit Jamie's body and become the laird once Sir James dies. However, the Intelligence is ultimately defeated by the Doctor. Jamie decides to leave the TARDIS and become the laird himself.
Given the acrimony between Haisman and Lincoln on the one hand and the BBC on the other hand, the Yeti, who had appeared in their earlier serials The Abominable Snowmen and The Web of Fear, were never again featured as the major antagonist in a televised Doctor Who story. However, a Yeti did make a brief cameo appearance in The Five Doctors, the series' twentieth anniversary special, in 1983. The Yeti and the Great Intelligence were the antagonists of the direct-to-video feature Downtime (1995), and the 2012 Christmas Special The Snowmen presented an origin for the Great Intelligence.