A major character is dead, Flame Princess battles Ice King in a mathematical battle of the elements and discover something in the aftermath. Then P-Bubs joins Marceline on a top-secret mission and takes a trip with Finn and Jake to the birthplace of BMO.
By any standard of inventiveness, intelligence, imagination, ambition, care, fearlessness, boldness, openness, humor, poetry and love I'd care to live my life by, it is as good as anything on television.
Adventure Time is one of the most philosophically risky and, often, emotionally affecting shows on TV. It's beautiful and funny and stupid and smart, in about equal parts, as well as willing to explore uneasy existential questions.