The Fellowship of the Ring: Being the First Part of the Lord of the RingsChapter 20
Gandalf Falls in Moria
Orcs and cave-troll attack in Chamber of Mazarbul; Gandalf confronts Balrog at Bridge of Khazad-dûm, shatters bridge, falls into abyss crying 'Fly, you fools!'
Outcome
Fellowship escapes leaderless under Aragorn.