Demonic pig spirit

The spirit of a demonically possessed Pig who possessed K-9, and made him attack Sarah Jane Smith. Long ago, a mighty demon, was banished to Earth, wandering disembodyied for eternity. It finally found corpeal form, possessing the pigs of a pig-pen outside the inn, the Sow in Rut. Through the pigs the demon made the managers of the inn, chop up the people staying at the inn and feed them to the pigs. Sarah Jane Smith investigated this decades later, after all the pigs had died, believing the ghost of one of the possessed pigs to have possessed K-9. Sarah was ultimately forced to damage K-9 to restore him to normality. This however was attributed to Brendan, who had been playing a computer game on K-9, a virus making K-9 take on the identity of the hog monsters from the game. This however proved not true, as the spirit of the possessed pig, lies in the darkness, eyes glowing red, wanting revenge on Sarah for banishing it from K-9, it's last hope at obtaining a corporeal form.... (ST: The Sow in Rut)