Based on a whimsical novel by Paul Gallico, Disney's Three Lives of Thomasina is an imaginative tale of a resourceful cat. Thomasina is the pet of Karen Dotrice, the daughter of taciturn Scottish veterinarian Patrick McGoohan.
When Thomasina falls ill, McGoohan coldly diagnoses the cat as suffering from tetanus and declares that the pet must be put out of its misery. As Dotrice and her friends sadly prepare to bury the dead Thomasina, backwoods girl Susan Hampshire, who is said to be a witch, shows up and runs off with the kitty corpse.
Using equal doses of intuition and love, Hampshire revives Thomasina, who of course wasn't dead at all. While in limbo, Thomasina ascends to Cat Heaven, where her case is heard by the Cat Goddess (this is a wonderful piece of special-effects wizardry, even if you don't like cats). Returned to life, Thomasina has no memory of her previous existence.
Thus, the cat runs off in terror when Dotrice sees her again during a torrential downpour. Now it is Dotrice who becomes seriously ill, necessitating a collaboration between the cold, cut-and-dried ministrations of her father and the tender loving care of the bewitched Hampshire.
As it turns out, Thomasina is the catalyst for both Dotrice's recovery and the film's happy ending.