Langwidere traps Dorothy in a painted prison, where she finds portals to other paintings by the same painter: Smith. Smith is one of Oz's most celebrated artists, widely praised for the realism of his paintings. Legend has it, he once painted a river that looked so real, he could swim in it.
Evelyn's painting depicts Dorothy's great grandmother (also named Dorothy) traveling down the Yellow Brick Road to Emerald City with a Lion, a Scarecrow, and a Tin Woodman. You can read more about their adventures together in L. Frank Baum's The Wonderful Wizard of Oz.