Simplify the following text for a Grade 6 native English-speaking person.
Original: At the end of Frankenstein 's narrative , Captain Walton resumes the telling of the story . A few days after Frankenstein has finished his story , the ship becomes entombed in ice and Walton 's crew insist on returning South once the ship is freed .
Simplified: Frankenstein went onto Captain Walton 's ship .