He's engulfed in a troublesome chasm
And the sulphur that bubbles there has him
Then a dynamite blast
Sets the swine free at last
With one awful great rubble-crumb spasm.
At the end of Son of Frankenstein (Rowland V. Lee; 1939), the monster falls into the sulphur pit beneath the castle. The story picks up from there in The Ghost of Frankenstein (Erle C. Kenton; 1942), the 4th entry in Universal's Frankenstein saga.